State v. Jule Hannah

SYLLABUS

This syllabus is not part of the Court’s opinion. It has been prepared by the Office

of the Clerk for the convenience of the reader. It has been neither reviewed nor

approved by the Court and may not summarize all portions of the opinion.

State v. Jule Hannah (A-44-24) (089819)

Argued October 9, 2025 -- Decided April 16, 2026

JUSTICE PIERRE-LOUIS, writing for a unanimous Court.

In this appeal, the Court considers whether a lay witness can testify regarding

cell site location information (CSLI) -- specifically, the locations of cell towers that

cell phones connect to -- or whether an expert witness is required.

Defendant Jule Hannah was charged with the murder of Miguez Lopez.

Detective Sergeant Kenneth Leyman obtained defendant’s cell phone records. The

State asserted at trial that these records supported its theory that Lopez picked

defendant up in Monroe Township and that the two men then crashed nearly an hour

later in Bridgeton, where Lopez was found shot to death. In addition to the phone

records, the State introduced the testimony of a forensic scientist that a cigar butt

found in Lopez’s car matched defendant’s DNA, as well as evidence of a recorded

phone call in which a third person can be heard in addition to Lopez and the caller.

Prior to defendant’s trial, the trial court allowed Detective Leyman to testify

as a lay witness regarding his use of phone records to map the locations of cell

towers that relevant cell phones, including defendant’s, connected to during the

pertinent time period surrounding Lopez’s death. In limiting the scope of Detective

Leyman’s testimony as a lay witness, the trial court stressed that there was to be no

testimony “about the location of any phone at any particular time.” The trial court

also gave several limiting instructions to the jury during Detective Leyman’s

testimony, directing that they should not consider CSLI alone as evidence that a

phone was in a particular place and advising that a cell phone’s connection to a cell

tower does not indicate whether the cell phone was in any particular location.

Despite the trial court’s instructions, Detective Leyman testified that the CSLI

could indicate where a suspect was at the time of Lopez’s death. His testimony also

associated the cell towers to which defendant’s cell phone connected to the path

Lopez traveled that day, consistent with the State’s theory that defendant was in

Lopez’s car prior to the homicide. Then, in summation, the State told the jury that a

cell phone must be close to the tower it connects to, stating that its proximity must

be “a stone’s throw” away.

1

The jury convicted defendant of first-degree murder and unlawful possession

of a weapon. The Appellate Division reversed defendant’s conviction, finding the

trial court erred in allowing Detective Leyman to testify about historical CSLI

without being qualified as an expert. The Appellate Division further concluded that

this inference carried significant weight in a case built largely on circumstantial

evidence, where the only physical link between defendant and the victim’s vehicle

was DNA on a cigar butt. The Appellate Division found the trial court’s limiting

instructions insufficient to cure the prejudice caused by Detective Leyman’s

testimony. The Court granted certification. 260 N.J. 214 (2025).

HELD: Pursuant to N.J.R.E. 702, CSLI involves technical and specialized

knowledge that must be presented to a jury by an expert witness at trial.

1. N.J.R.E. 701 provides the applicable standard for courts to determine the

admissibility of lay witness testimony. A lay witness may give an opinion on

matters of common knowledge and observation. When testimony requires an

opinion on a matter beyond common knowledge and observation, however, Rule 702

provides for the admission of expert testimony and discusses circumstances in which

an expert may testify. In case law, courts have identified circumstances in which an

expert -- as opposed to a lay witness -- must testify; that is, topics that can be raised

only if an expert will testify. In broad terms, when a subject is so esoteric that jurors

of common judgment and experience cannot form a valid conclusion, expert

testimony is required. A jury should not be allowed to speculate without the aid of

expert testimony in any area where laypersons could not be expected to have

sufficient knowledge or experience. Although expert witnesses may testify to

subjects that lay witnesses may not, their testimony must remain grounded in facts

or data derived from (1) the expert’s personal observations, or (2) evidence admitted

at the trial, or (3) data relied upon by the expert which is not necessarily admissible

in evidence but which is the type of data normally relied upon by experts. An

expert’s bare opinion that has no support in factual evidence or similar data is a

mere net opinion which is not admissible and may not be considered. (pp. 29-32)

2. The Court reviews how cellular networks operate, the relationship between cell

phones and cell towers, and the import of CSLI. The user’s proximity to a cell site

is significant in determining which tower has the strongest signal. However, the

strength of the signal is also influenced by the technical characteristics of the

towers; geography and topography; the angle and number of antennas; the features

of the phone itself; and environmental and geographical factors. Generally, courts

agree that an expert, not a lay witness, must present testimony regarding technical

aspects of cell towers and CSLI. Many courts, however -- including some that have

required expert testimony as to the technical aspects of CSLI -- have concluded that

a witness may provide limited testimony about the contents of call records detailing

the locations of cell towers utilized by a phone without being qualified as an expert.

2

But Maryland courts have rejected the argument that a layperson with the same

phone records and instructions could have determined the location of the cell sites

from such records. Although the Court has not previously considered whether CSLI

testimony must be offered by an expert, it recently held that expert CSLI testimony

that a defendant’s cell phone was likely near a crime scene was an inadmissible net

opinion because it lacked factual evidence or objective data. See State v. Burney,

255 N.J. 1 (2023). In Burney, the expert’s estimate of a cell tower coverage radius

was based solely on the agent’s personal “rule of thumb,” without reference to

supporting data, scientific calculations, or specific tower characteristics such as

height, power, or surrounding terrain. Id. at 5, 24-25. (pp. 32-41)

3. Here, the trial court’s repeated attempts to instruct the jury regarding CSLI -- see

pages 10 to 23 of the Court’s opinion -- illustrate the complexity of that testimony

and demonstrate exactly why such evidence must be presented by an expert witness.

A jury, properly informed about the intricacies and nuances of cell towers, should be

able to use CSLI to place a phone in a general area. But that cannot happen if a jury

is not properly equipped with the tools necessary to understand this relevant

evidence. Further, leaving the jury to draw any inferences it deemed appropriate

from the non-contextualized CSLI evidence -- without a full explanation of its

technical aspects and capabilities by an expert witness -- also risked confusing and

misleading the jury in violation of N.J.R.E. 403. Although a jury may be able to

figure out the location of cell towers using phone records, it would not be able to

draw any meaningful inferences from that information without an understanding of

how cell towers operate and why those cell tower locations matter. And, in the

absence of expert guidance, a jury could attribute more or less weight to the tower

locations than is warranted. The Court disagrees with the approach taken by many

jurisdictions -- allowing witnesses to provide limited testimony about the locations

of cell phone towers that cell phones connect to without being qualified as an expert.

The technical and specialized knowledge required to interpret CSLI is beyond the

ken of the average juror. Finally, the CSLI testimony that the jury heard in this case,

is at odds with Burney. If an expert attempted to offer the same conclusory

information that Detective Leyman did, that expert’s testimony would constitute an

impermissible net opinion in violation of N.J.R.E. 703 because the conclusions were

unsupported by adequate data. The State cannot circumvent the standards to which

expert testimony is held under N.J.R.E. 702 by presenting the testimony through a

lay witness rather than an expert. (pp. 41-47)

AFFIRMED.

CHIEF JUSTICE RABNER and JUSTICES PATTERSON, WAINER APTER,

FASCIALE, NORIEGA, and HOFFMAN join in JUSTICE PIERRE-LOUIS’s

opinion.

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SUPREME COURT OF NEW JERSEY

A-44 September Term 2024

089819

State of New Jersey,

Plaintiff-Appellant,

v.

Jule Hannah, a/k/a

Jule L. Hanna,

Defendant-Respondent.

On certification to the Superior Court,

Appellate Division.

Argued Decided

October 9, 2025 April 16, 2026

Bethany L. Deal, Deputy Attorney General, argued the

cause for appellant (Matthew J. Platkin, Attorney

General, attorney; Jeremy M. Feigenbaum, Solicitor

General, Michael L. Zuckerman, Deputy Solicitor

General, and Bethany L. Deal, and Nathaniel I. Levy,

Deputy Attorneys General, of counsel and on the briefs).

Stefan Van Jura, Assistant Deputy Public Defender,

argued the cause for respondent (Jennifer N. Sellitti,

Public Defender, attorney; Stefan Van Jura, of counsel

and on the briefs).

Maithreyi Nandagopalan (Innocence Project, Inc.) a

member of the New Mexico bar, admitted pro hac vice,

argued the cause for amici curiae American Civil

Liberties Union of New Jersey and the Innocence Project

1

(American Civil Liberties Union of New Jersey

Foundation and Innocence Project, Inc., attorneys; Dillon

Reisman, Ezra D. Rosenberg, Jeanne LoCicero, and

Maithreyi Nandagopalan, on the brief).

Lawrence S. Lustberg submitted a brief on behalf of

amicus curiae Association of Criminal Defense Lawyers

of New Jersey (Gibbons, attorneys; Lawrence S.

Lustberg, Anne M. Collart, and Jessica L. Guarracino, on

the brief).

Howard Pashman submitted a brief on behalf of amicus

curiae Larry E. Daniel, Executive Director of the Digital

Forensics Justice Initiative (Pashman Stein Walder

Hayden, attorneys; Howard Pashman and CJ Griffin, on

the brief).

JUSTICE PIERRE-LOUIS delivered the opinion of the Court.

In this appeal, we consider whether a lay witness can testify regarding

cell site location information (CSLI) -- specifically, the locations of cell

towers that cell phones connect to -- or whether an expert witness is required

to provide such testimony.

Prior to defendant Jule Hannah’s trial for murder and other offenses, the

trial court allowed Detective Sergeant Kenneth Leyman to testify as a lay

witness regarding his use of phone records to map the locations of cell towers

that relevant cell phones, including defendant’s, connected to during the

pertinent time period surrounding the victim’s death. In limiting the scope of

Detective Leyman’s testimony as a lay witness, the trial court stressed that

2

there was to be no testimony “about the location of any phone at any particular

time.” The trial court also gave several limiting instructions to the jury during

Detective Leyman’s testimony, directing that they should not consider CSLI

alone as evidence that a phone was in a particular place and advising that a cell

phone’s connection to a cell tower does not indicate whether the cell phone

was in any particular location.

Despite the trial court’s instructions, Detective Leyman testified that the

CSLI from the phone records could indicate where a suspect was during the

time of the victim’s death. His testimony also associated the cell towers to

which defendant’s cell phone connected on the morning of the victim’s death

to the path the victim traveled that day, consistent with the State’s theory that

defendant was in the victim’s car prior to the homicide. Then, in summation,

the State told the jury that a cell phone must be close to the tower it connects

to, stating that its proximity must be “a stone’s throw” away.

The jury convicted defendant of first-degree murder and unlawful

possession of a weapon. On appeal, the Appellate Division reversed

defendant’s conviction, finding the trial court erred in allowing Detective

Leyman to testify about historical CSLI without being qualified as an expert.

We granted the State’s petition for certification.

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For the reasons that follow, we affirm the judgment of the Appellate

Division and hold, pursuant to N.J.R.E. 702, that CSLI involves technical and

specialized knowledge that must be presented to a jury by an expert witness at

trial.

I.

We concentrate our recitation of the facts and procedural history on the

cell phone records at the heart of this appeal, relying primarily on the

testimony elicited at trial.

A.

On January 15, 2017, at approximately 8:30 a.m., a car crashed into a

tree on Spruce Street in Bridgeton. A witness observed a man with a distinct

limp and a puffy camouflage jacket quickly walking away down the road, and

neighbors found an unresponsive man in the driver’s seat.

A Bridgeton Police Department (BPD) officer arrived within five

minutes and found the vehicle -- a gold Chrysler Sebring -- with both the

driver and passenger side doors open. The driver, later identified as Miguel

Lopez, had been shot four times and had died from his wounds. During the

investigation, law enforcement learned that Lopez had been in Atlantic City

from about 3:30 a.m. until he left the casino in the gold Chrysler Sebring at

around 6:30 a.m. Video surveillance footage from various businesses along

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the route shows Lopez’s car traveling toward Bridgeton and arriving there

around 8:05 a.m.

As the officers investigated the death, they observed spent shell casings,

a bullet inside the vehicle, and ballistic evidence indicating that shots were

fired from the passenger side toward the driver’s side of the vehicle. Officers

also recovered a cigar butt with a plastic filter tip from the front passenger

seat.

One of the witnesses provided police with surveillance footage from her

residence that depicted the man she saw walking away from the scene. BPD

Detective Anthony Calabrese later testified he believed the man had a

distinctive limp in his left leg. Law enforcement initially identified two

potential suspects who were later deemed not to be involved in Lopez’s death.

One of the suspects communicated via text message with Lopez the morning of

his homicide and his palm prints matched those found in Lopez’s car. That

suspect was eliminated from consideration after his cell phone records showed

that his phone, during the relevant time period, connected to cell phone towers

in Millville. According to Detective Leyman, Millville was not in the general

proximity of the location in Bridgeton where Lopez was shot.

Detective Leyman testified that the footage from the witness’s home led

him to believe that defendant could be a suspect. Detective Leyman compared

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footage from the witness’s home of the suspect with the limp with footage

from an unrelated traffic stop in 2011 involving defendant and footage of

defendant from the Cumberland County Courthouse in 2017. Detective

Leyman testified at the pretrial hearing that he had previously interacted with

defendant on several occasions, including an arrest in 2009.

Investigators learned that at 7:27 a.m. on January 15, defendant’s cell

phone records showed a call to the Monroe Township Police Department. The

Monroe Township police relayed to Detective Leyman that defendant called to

report his involvement in a single car motor vehicle accident in the area of

Franklinville-Williamstown Road and Tuckahoe Road. At trial, the State

introduced testimony from James Burnett, an eyewitness to that crash.

According to Burnett, a Black man with a bald head approached his vehicle.

The man was walking with a limp and wearing a white tank top and cargo

shorts. Burnett testified that he did not observe the man to be wearing a

camouflage jacket. Burnett said the man offered him $100 to drive him to

Bridgeton. Burnett declined, and the man walked away. Burnett did not get a

good look at the man’s face and could not identify defendant at trial.

BPD sought and acquired a warrant to seize defendant’s cellular devices.

Detective Leyman later obtained the records, which showed the cell phone

towers defendant’s cell phone connected to on the day of Lopez’s homicide.

6

The State asserted at trial that these records supported its theory that Lopez

picked defendant up in Monroe Township around 7:30 a.m., after defendant’s

car accident, and that the two men then crashed nearly an hour later in

Bridgeton, where Lopez was found shot to death.

In addition to the phone records, the State introduced the testimony of a

forensic scientist that the cigar butt found in Lopez’s car contained DNA from

a single source that matched defendant’s DNA. The State further presented

evidence of a recorded phone call during the relevant time period in which a

third person can be heard in addition to Lopez and the caller.

B.

On March 14, 2018, a Cumberland County grand jury indicted defendant

on four counts related to Lopez’s homicide: (1) first-degree murder; (2)

second-degree possession of a weapon for an unlawful purpose; (3) second-

degree unlawful possession of a weapon; and (4) second-degree possession of

a weapon by a convicted person.

Prior to trial, the State moved to admit Detective Leyman’s testimony

regarding historical CSLI. Detective Leyman testified at a pretrial hearing that

he was prepared to describe which cell towers handled each call by

defendant’s cell phone that morning, including details such as the specific

antenna of each tower that the phone connected to and the antenna’s compass

7

direction, also known as its azimuth. The State initially sought to qualify

Detective Leyman as an expert in historical cell site analysis. The prosecutor

noted, “I have to qualify him as an expert in order for this testimony to come

in.”

Although Detective Leyman lacked formal training in

telecommunications or engineering, the State described him as an experienced

detective who had reviewed cell phone records on at least 75 different

occasions. Detective Leyman stated he had taken a course on “high tech

investigation” that covered cell phone records, and he had taught himself to

interpret phone records by consulting with phone carrier personnel. Further,

Detective Leyman testified that his four years in the United States Air Force

provided him with specialized training in mapping and directional navigation.

Detective Leyman stated that he learned through his military service how to

plot an azimuth.

When the State proceeded to question Detective Leyman on the facts of

the case, the defense objected on the basis that Detective Leyman’s stated

qualifications were insufficient for him to proceed as an expert witness. The

trial judge sought to clarify whether the State intended to present Detective

Leyman as an expert or lay witness. The State responded that it “would

proffer Detective Sergeant Leyman as an expert in the field of cell phone

8

record review, interpretation of cell tower data and plotting of cell tower data.”

The trial court directed the State to produce Detective Leyman’s curriculum

vitae and postponed a final ruling on whether he could testify as an expert.

The defense proceeded to cross-examine Detective Leyman on his

qualifications. Detective Leyman acknowledged that his experience with

historical cell site data derived primarily from on-the-job training, rather than a

formal curriculum. He again testified that he was able to interpret cell phone

records with the help of his military training and from conversations with cell

phone company representatives. After cross-examination, the defense renewed

its objection, arguing that the State sought to introduce expert testimony --

which requires a qualified expert witness -- and not simply a lay interpretation

of business records.

The trial court proposed that Detective Leyman could “say what the

record says.” In other words, he could read the data points from the cell phone

records and determine which cell phone tower antenna connected to

defendant’s phone. The defense protested, arguing that without an explanation

of the significance of CSLI -- e.g., that it could indicate the general location of

defendant’s phone -- testimony about this information would be irrelevant and

confuse the jury. The defense asserted that Detective Leyman’s testimony

about CSLI should be excluded under N.J.R.E. 403. The defense further

9

expressed concern that it would be unable to cross-examine Detective Leyman

about the potential implications of the cell data if the proposed testimony was

presented to the jury.

The trial judge expressed his willingness to allow Detective Leyman to

testify as a lay witness if his testimony was limited “to the location of the

towers and when the call hit that tower, not which antenna, not which direction

the antenna was pointed in, but just that tower.” The trial court allowed the

State to decide whether to attempt to qualify Detective Leyman as an expert,

stressing that “there’s not going to be any testimony about the location of any

phone at any particular time.” (emphasis added).

C.

Trial began on June 23, 2021. Before opening statements, the State

confirmed it would present Detective Leyman’s testimony “in a limited

capacity as a lay witness simply regarding the investigator’s review of the

records, interpretation of the records when it comes to the location of the cell

towers . . . and him plotting out the location of the cell towers on a map.” The

State added that it was “not going to have the officer testify in regards to the

antenna that was accessed or . . . the direction that the antenna was pointing

at.” The court responded:

[Y]ou must be clairvoyant [be]cause my decision I was

going to give you today is I’m not going to permit the

10

officer to testify about the direction of any antenna or

the azimuth of any antenna nor his interpretation of the

identification of any particular antenna on any tile --

tower. Okay. We discussed that at length yesterday.

The court agreed to “permit lay person testimony with regard to the location of

the tower and the time when the tower connected the call.”

The trial judge went on to further limit the scope of Detective Leyman’s

testimony, focusing on curbing the use of CSLI for the purpose of tracking

defendant’s movements on the morning of Lopez’s death:

I’m not going to permit testimony about the cell tower

location upon the termination of the call unless there is

significant distance between the start and ending of the

call because the switching between the towers is not

necessarily confined solely to the distance traveled by

an individual on the phone. Cell tower switching is a

complicated issue, depends on signal strength. We

don’t have an expert to testify as to why a tower may

switch.

....

I think it’s clear that in order to get any directional data

from a cell tower dump you’re going to need an expert

to explain to the jury how the cell tower works.

Soon thereafter, the court issued an order regarding Detective Leyman’s

testimony. The order stated that “the parties stipulate” that Detective Leyman

“shall be permitted to provide only lay witness testimony regarding his review,

interpretation, and plotting of the location of cell towers on a map from the

defendant’s historical cell site data records” and specified that “[t]here shall be

11

no testimony concerning the azimuth of any antenna or any cell tower sector

accessed by any call within the defendant’s call detail records.” 1 Finally, the

order provided that the State could offer testimony about “the cell phone tower

indicated at call termination” “without further order from the Court,” but

“[o]nly when the same cell tower was utilized for a cell phone call’s

origination and termination.”

On June 25, 2021, Detective Leyman testified regarding the CSLI

obtained during the investigation. The State asked Detective Leyman whether,

in his “training and experience,” he had “been able to learn how to read phone

records, call detail records, and the information contained therein,” to which

he responded affirmatively. When asked whether those records include “an

indication . . . as to what cell tower the phone would have access to,” Detective

Leyman replied, “[y]es.” Detective Leyman then testified that the phone call

records denote the time that a cell tower is accessed. He explained, in the

following exchange with the State, the information those records may provide

regarding a user’s location:

STATE: And would those phone records have provided

information regarding where [one of the initial

1

“Call detail records” are records that include “the phone numbers dialed out

from [a] cell phone, the phone numbers dialed in to that phone, and the date,

time, and duration of those calls.” State v. Lunsford, 226 N.J. 129, 133

(2016).

12

suspects] may have been located at the time that the

homicide occurred?

LEYMAN: Yes.

....

STATE: In particular, whenever a phone call is made

or received, again, would that phone have to connect to

a tower in order to make or receive the phone call?

LEYMAN: Yes.

STATE: And would that tower provide a -- a

approximate location as to where that phone may have

been located at the time?

LEYMAN: Yes.

[(emphases added.)]

Detective Leyman testified that the initial suspect placed calls around the time

of the homicide that connected to a cell tower that was not near the location of

the crime scene.

Later during his testimony, Detective Leyman testified about defendant’s

cell site data from the morning of Lopez’s death. The State introduced

redacted records provided by Sprint regarding defendant’s phone that morning,

which were displayed to the jury. Detective Leyman indicated that he had

reviewed cell phone records from Sprint before. He described how to interpret

each line item from the records by explaining how to determine whether

entries represented a phone call or a text message; the number that initiated the

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call or text; the number that received the call or text; whether the call

connected; the duration of the call; and which cell towers the phone connected

to at the beginning and end of each call.

The State then asked whether Detective Leyman “ha[d] an opportunity to

essentially plot out and determine what tower was being accessed [by

defendant’s phone] when certain incoming and outgoing calls were made

during” the relevant time period of Lopez’s death, to which he responded,

“[y]es.” The State proceeded to walk through defendant’s phone records with

Detective Leyman and discussed the call entries, including the starting and

ending time of the calls and location of each cell tower to which defendant’s

phone connected. After Detective Leyman reviewed two records, the trial

judge indicated that he wanted to give a limiting instruction regarding the

detective’s testimony. The trial judge provided the following instruction:

All right. Ladies and gentlemen, you’ve heard some

testimony here about a call connecting to a cell phone

tower at a particular time and a particular location. In

conjunction with that the State has also shown you a

location where someone was purported to be or an event

was purported to have happened sometime relevant to

the proceedings here. I want to make it clear to you that

while they can show you those locations and how far

apart they are that evidence does not establish where

that phone was at any -- at that time that that call

connected.

Do you understand? It doesn’t -- just because there is

a cell tower somewhere proximate to something else

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doesn’t mean that that phone was located any particular

spot within any particular distance from that tower.

Does everybody understand that? So that is -- you

should not consider that that evidence was that phone

was there or here or any other particular place, only that

there was a call received at that location and that at the

same time something else was happening at another

location and they were so far apart.

But that’s for you to determine, you know, where that

information might be considered in the decisions you

need to make here. But that fact that there was a phone

call received at that tower does not mean that phone was

in any particular location. You understand? So all you

know is that a call connected at a certain time at that

location and there was something else that happened

somewhere around there. That doesn’t mean that that

phone was in any particular spot at the time that that

phone call was made? Okay? All right.

Testimony resumed and the State continued to question Detective

Leyman about the call records. For each record, the prosecutor attempted,

through questioning of Detective Leyman, to draw a connection between the

call entry and a relevant location, such as defendant’s motor vehicle crash

before the homicide:

STATE: And, again, I won’t go through it again

because we already pulled it up previously. But that

tower from what you could tell in your review was in

close proximity to the location of the defendant’s motor

vehicle crash?

LEYMAN: Approximately 3,000 feet, yes.

15

STATE: Okay. And the call would have connected to

that tower at the same time he would have allegedly, or

yes, been in that area?

THE COURT: I want to strike that question. Ladies

and gentlemen, you cannot infer simply by looking at

where a tower is and where a phone call may have been

made at that that where the call originated from and

therefore connected to that tower.

STATE: And, judge, respectfully, that -- that what --

I’ll rephrase the question.

THE COURT: You better rephrase that question,

counsel.

STATE: The tower that the phone connected to is

approximately 3,000 feet away from the site of the

location, correct?

LEYMAN: Yes.

As the prosecutor and Detective Leyman continued discussing call

entries, the prosecutor repeatedly asked whether “directionally speaking,” the

cell tower utilized by the call being discussed was “north or south of the last

tower that was accessed.” Altogether, the prosecutor asked Detective Leyman

about 16 call entries, each time comparing the data to the known locations of

the victim’s vehicle at the time that the call was placed.

The next trial day, before Detective Leyman’s cross-examination began,

the court issued another limiting instruction regarding the prior CSLI

testimony:

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Now, you recall last week there was some testimony

concerning cell tower and cell tower locations. And I

-- when that testimony came up I gave you what we call

limiting instruction with regard to that. I’m going to

give you a similar limiting instruction. It’s on the same

issue. Doesn’t change what I told you last week. It

may just clarify it. Okay. So pay attention here.

There was testimony regarding the location of cell

phone towers which connected phone calls from a

particular phone. You may not use the location of the

cell phone tower to determine the location of the phone

making the phone which connected to the tower. The

location of any particular phone at any particular time

is a question -- is a question of is an independent -- I

think what they meant to say was that’s an independent

question of fact that you must decide for yourself.

Do you understand? So the cell tower going off right

there does not mean that cell is in any particular spot,

which is what I told you. You have to -- if you -- if you

need to determine that fact, you determine it from all

the facts, you understand, not just that that cell tower

went off. You understand? That cell tower doesn’t tell

you that that phone was there or there. It tells you the

phone connected that cell tower. That fact and any

other facts you can use if you need to determine where

a phone may or may not have been. But a cell tower

location doesn’t establish that it was in any particular

spot. Does everybody understand that? Okay. All

right.

On cross-examination, defense counsel pressed Detective Leyman on the

types of information CSLI cannot provide:

DEFENSE: So let’s talk about the cell towers. So now

we’ve agreed that the cell phone records can’t tell us

who -- first of all, they don’t tell us what person

actually had that phone in their hand, correct?

17

LEYMAN: That’s correct.

DEFENSE: We just know the phone number, right, not

the actual phone.

LEYMAN: Yes.

DEFENSE: All right. And you would agree that you

can’t tell the location of the phone just based upon the

tower that the call connected to, right?

LEYMAN: Exact location, no.

DEFENSE: And you would agree that the records

reflect that the tower that the phone connected to which

is not necessarily the tower that is closest to the actual

phone, correct?

LEYMAN: Correct.

DEFENSE: And the phone records do not reflect any

distance of the phone in proximity to the tower, correct?

You don’t get that from the records.

LEYMAN: Correct.

Defense counsel confirmed with Detective Leyman that, between 8:07

a.m. and 9:37 a.m. on the day of the homicide, defendant’s phone connected to

tower 37 -- located on the corner of Commerce Street and Pearl Street in

Bridgeton -- 16 times. Detective Leyman clarified that defendant’s phone also

connected to a second tower at 8:50 a.m. -- tower 304. On re-direct, the State

and Detective Leyman had the following exchange:

18

STATE: So the tower’s hitting off of -- or strike that.

The defendant’s phone is hitting off of tower 37 before,

during and immediately after the homicide, is that fair?

LEYMAN: Yes.

....

STATE: So just to go through that again briefly. The

tower that we’re talking about, is that located right

there?

LEYMAN: Yes.

STATE: And the defendant’s residence, 35 Reeves

Road.

LEYMAN: Yes.

STATE: And, again, the scene of the crime, 406 Spruce

Street.

LEYMAN: Correct.

STATE: And to be clear, is both the defendant’s

residence and the scene of the crime in proximity to the

cell phone tower in question?

LEYMAN: Yes.

....

STATE: And you also indicated that there was a point

in time -- what was that time again where the tower --

the phone hits off of the tower 304?

LEYMAN: 8:50 and 42 seconds in the morning.

STATE: And what is the latitude and longitude of that

tower?

19

LEYMAN: Latitude 39.392194 by longitude negative

75.216329.

STATE: Now, is that tower located towards the area

the suspect is seen walking or away from the area the

suspect is seen walking?

LEYMAN: Toward.

The trial judge subsequently provided his third limiting instruction on

Detective Leyman’s testimony with respect to CSLI:

Ladies and gentlemen, before we go on I’m going to

give you another one of those limiting instructions.

Okay. Please follow along. It’s along the lines of what

we talked about before. Has to do with the cell tower.

Okay. You heard some testimony that a -- that a call

referenced in this information may have switched from

one cell tower to another cell tower. Now, that

information alone is insufficient to prove the phone

moved. Do you understand? So simply that alone, you

can’t say that phone went anywhere when it switched

from one tower to another tower. However, in

conjunction with other evidence you may -- you may

reach a conclusion -- you’re not prohibited, but if it’s

just that it switched you can’t use that to conclude that

cell phone moved. Does everybody understand? Okay.

Very well.

Detective Leyman’s testimony concluded the State’s case-in-chief.

During summation, the State argued that “[c]ommon experience dictates that

you have to be close to a [cell] tower in order to connect to a call.” The

prosecutor then told the jury:

20

[C]ontrary to what [defense counsel] told you, this is

one way that you can confirm that when a call is made

is received that phone has to be close to the tower that’s

being accessed. I’d say it’s a stone’s throw. That’s

maybe a bit of an exaggeration. I don’t know if

anybody has that good of an arm. But if you recall from

Detective Leyman’s testimony, he indicated is

approximately a mile, if not a mile and a half, between

those two locations. 2

[(emphasis added.)]

The State further argued that defendant’s phone was “clearly moving with the

victim because it’s hitting off of towers [in] the same direction that the victim

is traveling” and that “it’s a fair conclusion that the defendant was in

proximity to all of the towers, all of the towers that you see where he’s

moving.”

Defense counsel objected to the prosecution’s closing argument,

specifically the references to the cell phone tower evidence. The defense

stressed that, in its June 24, 2021 order, the court had ruled that the mere

location of a cell tower cannot be used as evidence to determine the actual

location of a phone or person in the case. Defense counsel acknowledged that

the prosecutor at times noted that cell phone data could be used alongside

other evidence, including surveillance footage and photographs, to reach a

2

The two locations the prosecutor referenced were the site of defendant’s

single-vehicle accident and the cell tower that defendant’s cell phone

connected to around the time of that accident.

21

conclusion about defendant’s location. However, defense counsel objected to

instances in which the prosecutor implied that the jury could determine

defendant’s location based solely on tower location. The trial judge responded

that, while cell phone tower data alone does not establish location, it may do

so in conjunction with other evidence.

Defense counsel further objected to the prosecutor’s argument in

summation that “the [defendant’s] phone is clearly moving with the victim

because it’s hitting off of towers the same direction that the victim is

travelling.” Counsel asserted that such conclusions were impermissible

without supporting evidence. The trial judge disagreed, stating that it was not

“beyond the ken of an average juror to realize that the closer you’re to a tower

. . . the stronger your signal is.”

During the final jury charge, the trial judge provided additional

instructions to the jury regarding CSLI:

During the trial you heard testimony about phone calls

connected to cell towers that were providing --

provided information as to the location of a certain cell

tower accessed during that call. In any case where a

particular call started connected to one tower and

switched to a different tower you may not conclude

from that information alone that the cell phone changed

position or moved in any particular direction. If you

believe it is appropriate to do so, you may, however,

consider that fact with -- along with other facts that you

may find relevant to the issue of whether a cell phone

moved or if it moved in any specific direction. But you

22

cannot reach a conclusion about the movement of a cell

phone based only upon the fact that a call switched

between towers.

Now, ladies and gentlemen, that same principle applies

to a series of calls. You understand? You cannot

conclude, and I think I -- I don’t know whether that

instruction got in here or not, but you can’t conclude

that a phone was in any particular spot simply because

it connected to a tower. You can, however, utilize that

information along with other information if you think

it’s appropriate to do so. You understand?

But that information alone doesn’t mean that cell phone

was in any particular spot. You’d have to have other

evidence to rely upon and you could use that evidence

in conjunction with it. Do you understand what I’m

saying? So the cell phone tower alone just cause it’s

hitting off that tower doesn’t mean it’s in any particular

spot. There has to be -- you’d have to be relying on

some other evidence in connection with that to make

that determination. Does everybody understand this?

And, again, that’s if you believe it is appropriate to do

so. You understand? You’re the finders of fact. You

decide whether or not that’s relevant to what you --

what you’re determining.

D.

The jury found defendant guilty of first-degree murder, unlawful

possession of a weapon, and possession of a firearm with an unlawful purpose.

Defendant moved for a new trial, arguing that Detective Leyman’s testimony

exceeded the bounds of the court’s order. The trial judge denied the motion,

stating that Detective Leyman reiterated rather than interpreted the cell tower

information; that “[t]he correlation with regard to direction and location were

23

done through other evidence” and were not “improper”; and that a jury could

“infer that the phone was traveling along this road -- [R]oute 77 and as it

traveled along cell tower information they could rely upon to say, okay, the

cell tower rang up that phone at some point or was in contact with that phone.”

The trial court sentenced defendant to a 45-year prison term on the

murder conviction, subject to an 85% parole ineligibility period pursuant to the

No Early Release Act, and a concurrent sentence of 10 years in prison with

five years of parole ineligibility for unlawful possession of a weapon.

E.

On appeal, defendant argued that the admission of historical cell site

data through lay witness testimony, rather than expert testimony, was improper

and violated his right to a fair trial. The Appellate Division agreed and

reversed and remanded for a new trial, holding that the trial court erred by

permitting historical CSLI to be introduced through lay testimony rather than

through a qualified expert. Although the trial court denied the State’s request

to admit Detective Leyman as an expert, it nevertheless permitted him to offer

testimony interpreting and mapping the locations of cell towers accessed by

defendant’s phone. The appellate court found that this testimony went beyond

the permissible scope of lay witness opinion and addressed a central factual

24

issue in dispute: whether defendant was in the victim’s vehicle around the

time of the shooting.

The Appellate Division further concluded that this inference carried

significant weight in a case built largely on circumstantial evidence, where the

only physical link between defendant and the victim’s vehicle was DNA on a

cigar butt. The Appellate Division found the trial court’s limiting instructions

insufficient to cure the prejudice caused by Detective Leyman’s testimony.

We granted the State’s petition for certification. 260 N.J. 214 (2025).

We also granted leave to appear as friends of the court to the American Civil

Liberties Union of New Jersey and the Innocence Project, Inc. (jointly,

ACLU), the Association of Criminal Defense Lawyers of New Jersey (ACDL),

and Larry E. Daniel, Executive Director of the Digital Forensics Justice

Initiative.

II.

The State asks this Court to reverse the Appellate Division’s decision.

The State argues that Detective Leyman properly testified about the cell phone

tower locations as a lay witness. The State asserts that the trial court accepted

the parties’ stipulated agreement 3 and permitted Detective Leyman to testify in

3

A party that stipulates or consents to the admission of certain evidence at

trial may sometimes be prohibited from objecting to that evidence on appeal

under the invited error doctrine. See DYFS v. M.C. III, 201 N.J. 328, 340-42

25

a manner consistent with other courts across the country that have confronted

the same issue. According to the State, cell towers listed in phone company

records can be identified through lay testimony because determining the

location of cell towers that a particular cell phone connected to does not

require expertise. The State further contends that a jury is free to draw

reasonable inferences from this testimony.

Defendant argues that specialized expertise is necessary to interpret

historical CSLI and describes the language in the Sprint cell phone records as

“bewildering” and full of technical “jargon.” He asserts that a layperson

would have difficulty determining the geographic coordinates of a cell tower

to which a phone connected and would be unable to draw meaningful

conclusions from the records without expert guidance. Defendant also argues

that testimony about cell tower locations, without explanation of their

coverage area, is misleading and should be proscribed under N.J.R.E. 403.

(2010). The doctrine in part serves to bar litigants “from raising an objection

for the first time on appeal.” State v. A.R., 213 N.J. 542, 561 (2013). The

invited error doctrine, however, does not apply here. As the State recognized

during oral argument before this Court, defense counsel preserved this issue

for appeal through a timely objection at trial. Specifically, defense counsel

stated the following on the record: “I wanted to preserve for the record that all

my objections to those records that we previously dealt with through in limine

motions and objections . . . I’m not waiving any of those prior arguments or

objections by consenting to the admission of the records today.”

26

Several amici curiae support defendant’s position and argue that an

expert should be required to testify about raw CSLI data when used to locate a

phone. The ACLU argues that CSLI cannot accurately pinpoint a phone’s

location -- it can only indicate that a phone was somewhere within a cell

tower’s broad coverage area, which can extend for miles. The ACLU asserts

that jurors are unlikely to understand the technical limits of CSLI and that

limiting instructions are insufficient to cure potential prejudice or confusion.

According to the ACLU, when the State fails to produce an expert for this

testimony, defendants are deprived of an opportunity to meaningfully cross-

examine a witness about the limits of CSLI.

Amicus curiae Larry E. Daniel argues that phone call records do not

directly establish a phone’s location or proximity to towers and emphasizes the

risk of overstating the precision of such evidence. Daniel conveys that many

factors -- such as natural terrain, buildings, weather, antenna strength and

height, network load balancing, technical capabilities of the phone, and

equipment malfunction or installation errors -- can cause a phone to connect to

a more distant site than the closest cell tower. Daniel asserts that experts are

needed to explain the implications and limitations of CSLI to ensure that the

factfinder is not misled by oversimplified conclusions.

27

Similar to Daniel, the ACDL argues that conclusions cannot be drawn

about a cell phone’s location based on call records without consideration of

numerous variables -- an analysis that is not within the ken of the average

juror. The ACDL argues that the interpretation and explanation of call detail

records is itself a technical task that requires an expert with specialized

knowledge and training.

III.

A.

We review a trial court’s evidentiary rulings for abuse of discretion.

State v. Allen, 254 N.J. 530, 543 (2023). We do not substitute our judgment

for that of the trial court “unless the evidentiary ruling is ‘so wide of the mark’

that it constitutes ‘a clear error in judgment.’” State v. Garcia, 245 N.J. 412,

430 (2021) (quoting State v. Medina, 242 N.J. 397, 412 (2020)).

Regarding limiting instructions from a trial court, we have

acknowledged that, “in appropriate cases,” “a proper limiting instruction can

cure any potential juror confusion” about admitted evidence. Hrymoc v.

Ethicon, 254 N.J. 446, 474 (2023). When limiting instructions themselves are

incomplete or unclear, however, they can compound the prejudice caused by

erroneous evidentiary determinations. See, e.g., State v. Jones, 425 N.J. Super.

258, 276 (App. Div. 2012); see also State v. Sanchez-Medina, 231 N.J. 452,

28

465 (2018) (holding that the trial court compounded the prejudice caused by

the erroneous admission of defendant’s immigration status by issuing

conflicting and incomplete instructions regarding the permissible use of that

evidence).

B.

Pursuant to N.J.R.E. 401, “relevant evidence” is defined as evidence

having “a tendency in reason to prove or disprove any fact of consequence to

the determination of the action.” Relevancy is a combination of “probative

value and materiality.” State v. Higgs, 253 N.J. 333, 358 (2023) (quoting State

v. Buckley, 216 N.J. 249, 261 (2013)) (internal quotations omitted). Relevant

evidence is admissible only if no exception applies. N.J.R.E. 401, 402. One

such exception is N.J.R.E. 403(a), which provides that “relevant evidence may

be excluded if its probative value is substantially outweighed by the risk of . . .

[u]ndue prejudice, confusing the issues, or misleading the jury.” Those rules

apply to all evidence, including the testimony of lay and expert witnesses.

N.J.R.E. 701 provides the applicable standard for courts to determine the

admissibility of lay witness testimony. State v. Sanchez, 247 N.J. 450, 466

(2021). The rule states that a non-expert witness’s “testimony in the form of

opinions or inferences may be admitted if it: (a) is rationally based on the

29

witness’[s] perception and (b) will assist in understanding the witness’[s]

testimony or determining a fact in issue.” N.J.R.E. 701.

As this Court has noted in the past, “[t]here are, however, limits that

have traditionally been imposed on lay opinion testimony.” State v. McLean,

205 N.J. 438, 459 (2011). Specifically, N.J.R.E. 701 “does not permit a

witness to offer a lay opinion on a matter ‘not within [the witness’s] direct ken

. . . and as to which the jury is as competent as [the witness] to form a

conclusion.’” Ibid. (quoting Brindley v. Firemen’s Ins. Co., 35 N.J. Super. 1,

8 (App. Div. 1955)). This Court has recognized that a “lay witness may give

an opinion on matters of common knowledge and observation.” State v.

Bealor, 187 N.J. 574, 586 (2006) (quoting State v. Johnson, 120 N.J. 263, 294

(1990)).

When testimony requires an opinion on a matter beyond “common

knowledge and observation,” however, Rule 702 provides for the admission of

expert testimony. N.J.R.E. 702 states:

If scientific, technical, or other specialized knowledge

will assist the trier of fact to understand the evidence or

to determine a fact in issue, a witness qualified as an

expert by knowledge, skill, experience, training, or

education may testify in the form of an opinion or

otherwise.

Rule 702 discusses circumstances in which an expert may testify. In

case law, courts have identified circumstances in which an expert -- as

30

opposed to a lay witness -- must testify; that is, topics that can be raised only if

an expert will testify. In broad terms, “when ‘a subject is so esoteric that

jurors of common judgment and experience cannot form a valid conclusion,’”

“expert testimony is required.” Hopkins v. Fox & Lazo Realtors, 132 N.J. 426,

450 (1993) (quoting Wyatt by Caldwell v. Wyatt, 217 N.J. Super. 580, 591

(App. Div. 1987)); see also Biunno, Weissbard & Zegas, Current N.J. Rules of

Evidence, cmt. 2 on N.J.R.E. 702 (2025) (“[A] jury should not be allowed to

speculate without the aid of expert testimony in any area where laypersons

could not be expected to have sufficient knowledge or experience.”).

Applying that rule, courts have required expert testimony in certain

cases. In Wyatt, for example, the Appellate Division held that, in an

automobile negligence case, eyewitness lay testimony about brake fluid and

brake pad condition was improper without expert testimony linking those

observations to the alleged brake failure. 217 N.J. Super. at 591-92. And in

Taing v. Braisted, the trial court ruled that the complex factors affecting

whether a car’s airbag deploys in an accident -- including the amount and

direction of force and the operation of airbag sensors -- require expert

explanation, and that lay testimony alone is insufficient for a jury to

understand or determine the relevance of airbag deployment. 456 N.J. Super.

465, 469-71 (Law Div. 2017); see also Morales-Hurtado v. Reinoso, 457 N.J.

31

Super. 170, 193 (App. Div. 2018) (holding that lay testimony regarding

whether airbags deployed in a rear-end collision was inadmissible because an

expert was needed to determine whether airbags are engineered to deploy in

such collisions and that, without an expert, such testimony “might have been

misleading”).

Although expert witnesses may testify to subjects that lay witnesses may

not, their testimony must remain “grounded in facts or data derived from (1)

the expert’s personal observations, or (2) evidence admitted at the trial, or (3)

data relied upon by the expert which is not necessarily admissible in evidence

but which is the type of data normally relied upon by experts.” Townsend v.

Pierre, 221 N.J. 36, 53 (2015) (quotation omitted). “[A]n expert’s bare

opinion that has no support in factual evidence or similar data is a mere net

opinion which is not admissible and may not be considered.” Pomerantz Paper

Corp. v. New Cmty. Corp., 207 N.J. 344, 372 (2011).

C.

We briefly describe how cellular networks operate, the relationship

between cell phones and cell towers, and the import of CSLI.

“Cellular networks are comprised of many cells (colloquially ‘towers’),

containing antennas, cell electronics, and links to the network controlling

computers located at each network operator’s regional offices.” Vladan M.

32

Jovanovic & Brian T. Cummings, Analysis of Mobile Phone Geolocation

Methods Used in US Courts, 10 IEEE Access 28037, 28037 (2022). A cell

phone connects to this network “like a scanning radio” and “use[s] radio waves

to communicate between a user’s handset and a telephone network.” State v.

Earls, 214 N.J. 564, 576 (2013). “To connect with the local telephone

network, the Internet, or other wireless networks, cell-phone providers

maintain an extensive network of cell sites, or radio base stations, in the

geographic areas they serve.” Ibid. When a cell phone user places a call or

sends a text message, the phone generally “connects to the cell site with the

strongest signal.” Aaron Blank, The Limitations and Admissibility of Using

Historical Cellular Site Data to Track the Location of a Cellular Phone, 18

Richmond J.L. & Tech. 1, 5 (2011).

The user’s proximity to a cell site is significant in determining which

tower has the strongest signal. Earls, 214 N.J. at 576. However, the strength

of the signal is also influenced by the technical characteristics of the towers;

geography and topography; the angle and number of antennas; the features of

the phone itself; and “environmental and geographical factors.” United States

v. Hill, 818 F.3d 289, 295-96 (7th Cir. 2016) (quoting Blank, 18 Richmond J.

L. & Tech. at 7). “Unlike the more precise location data provided by a Global

Positioning System (GPS), cell site analysis simply confirms that the phone

33

was somewhere within the coverage radius of the cell tower during the

recorded activity.” State v. Burney, 255 N.J. 1, 22 (2023) (citing James Beck

et al., The Use of Global Positioning (GPS) and Cell Tower Evidence to

Establish a Person’s Location -- Part II, 49 Crim. L. Bull. 637, 645 (2013)).

Historical CSLI can be useful in determining a phone user’s geolocation.

For instance, it can help “identify the general area [where] the target mobile

phone number is located at the time of a specific call,” even if it “cannot

pinpoint the exact location of the mobile phone.” In re Application for Ord.

Authorizing Pen Register, 415 F. Supp. 2d 211, 213 n.3 (W.D.N.Y. 2006)

(quoting a Verizon representative). “Individual cell[ towers] can cover

distances from a fraction of [a] mile to many miles and are usually split in

sectors. Sectors are split up areas around the cell covered by their own

directive antennas.” Jovanovic, 10 IEEE Access at 28037-38.

Generally, courts agree that an expert, not a lay witness, must present

testimony regarding technical aspects of cell towers and CSLI. See, e.g., Hill,

818 F.3d at 299; State v. Boothby, 951 N.W.2d 859, 876 (Iowa 2020); State v.

Sinnard, 543 P.3d 525, 544 (Kan. 2024); State v. Wyman, 107 A.3d 641, 647-

48 (Me. 2015); State v. Payne, 104 A.3d 142, 154-55 (Md. 2014).

Many courts, however -- including some that have required expert

testimony as to the technical aspects of CSLI -- have concluded that a witness

34

may provide limited testimony about the contents of call records detailing the

locations of cell towers utilized by a phone without being qualified as an

expert. See, e.g., United States v. Graham, 796 F.3d 332, 365-66 (4th Cir.

2015) (holding that testimony regarding a map of cell sites to which a cell

phone connected “did not amount to an expert opinion” because mapping

“required little more than identification of the various locations” drawn from

records), rev’d on other grounds, 824 F.3d 421 (4th Cir. 2016) (en banc);

Boothby, 951 N.W.2d at 878 (allowing testimony limited to identifying the

location of cell towers pinged by the defendant’s phone because it was based

on “factual information obtained from [phone] records rather than any

specialized knowledge about how cell towers operate”); Sinnard, 543 P.3d at

544 (permitting lay testimony “so long as the witness does not” provide a

“technical opinion regarding . . . the location of a cell phone at a particular

time, . . . [or] an explanation as to why a cell phone connected to a specific cell

tower over another”); Torrence v. Commonwealth, 603 S.W.3d 214, 228 (Ky.

2020) (“[M]arking points on a graph -- in these cases a map -- based on a cell

phone report including latitude and longitude of cell towers, does not require

an expert.”); State v. Blurton, 484 S.W.3d 758, 771 (Mo. 2016) (“‘[R]eading

the coordinates of cell sites from phone records and plotting them on a map is

not a scientific procedure or technique’ because cell phone records are factual

35

records and no special skill is required to plot these records.” (quoting State v.

Patton, 419 S.W.3d 125, 130 (Mo. App. 2013))); Burnside v. State, 352 P.3d

627, 636 (Nev. 2015) (holding that detective’s testimony about a map he

created to plot cell phone tower locations was admissible lay testimony);

Wyman, 107 A.3d at 648 (“A witness need not be an expert to explain that the

timing column on a cell phone billing record refers to the time at which a call

was made or received, or to explain that the ‘origination’ column refers to the

location of the cell tower used by a phone to make or receive a call.”).

Maryland courts have reached a different conclusion. In Payne, the

defendant and his co-defendant were convicted of felony murder, kidnapping,

and use of a handgun in the commission of a felony. 104 A.3d at 143. At

trial, a police detective testified that by interpreting Payne’s cell phone

records, he was able to plot the location of cell phone towers that defendant’s

phone connected to on a map in relation to the crime scene. Ibid. Defense

counsel objected, arguing that this testimony required an expert. Ibid.

Rejecting the State’s argument that a “layperson with the same phone

records and instructions could have determined the location of the cell sites,”

the Supreme Court of Maryland determined that a “Call Detail Record contains

a string of data unfamiliar to a layperson” and the State’s witness relied on his

specialized knowledge to understand the record’s “technical language” to

36

“hone in on the entries . . . ‘pertinent’ to the case,” and “eliminate ‘extraneous’

data.” Id. at 154. The court held that “additional training and experience were

required to parlay the process from which [the State’s witness] derived the

communication path of each call.” Id. at 155. Ultimately, the Maryland court

held that by “merely read[ing] Sprint Nextel’s business records and

follow[ing] its directions in interpreting the data,” the State’s expert engaged

in a process “beyond the ken of an average person” in order to conclude that

the defendant’s phone communicated with particular cell towers. Id. at 154;

see also Wilder v. State, 991 A.2d 172, 197 (Md. App. 2010) (noting the

appropriateness of “preserv[ing] the distinction between lay and expert opinion

testimony,” in part to “ensure[] that a party will not evade the expert witness

disclosure requirements . . . by simply calling an expert witness in the guise of

a layperson”).

Although this Court has not previously considered whether CSLI

testimony must be offered by an expert, we recently addressed CSLI testimony

in considering whether expert testimony that a defendant’s cell phone was

likely near a crime scene was an inadmissible net opinion. Burney, 255 N.J. at

25. In Burney, the prosecution’s expert, an FBI special agent, testified that the

coverage radius of a relevant cell tower was approximately one mile, placing

defendant’s cell phone near the crime scene at the time of a nighttime home

37

invasion and robbery. Id. at 5. That estimate was based solely on the agent’s

personal “rule of thumb” for towers in the area, without reference to

supporting data, scientific calculations, or specific tower characteristics such

as height, power, or surrounding terrain. Id. at 5, 24-25. The defense argued

that the agent’s “rule of thumb” methodology was unreliable and constituted a

net opinion because it lacked factual evidence or objective data. Id. at 24. We

agreed and held that the testimony was an inadmissible net opinion that should

not have been presented to the jury. Id. at 25.

This Court noted in Burney that the Seventh Circuit has recognized the

possibility that a “‘jury may overestimate the quality of the information

provided by’” cell site data analysis and has “admonished that ‘[t]he admission

of historical cell-site evidence that overpromises on the technique’s precision

-- or fails to account adequately for its potential flaws -- may well be an abuse

of discretion.’” Id. at 22 (quoting Hill, 818 F.3d at 299). In Hill, the Seventh

Circuit cautioned the Government against “present[ing] historical cell-site

evidence without clearly indicating the level of precision -- or imprecision --

with which that particular evidence pinpoints a person’s location at a given

time.” Hill, 818 F.3d at 299. In that case, the court ultimately concluded that

admission of the expert’s testimony was not an abuse of discretion because he

“made the jury aware not only of the technique’s potential pitfalls, but also of

38

the relative imprecision of the information he gleaned from employing it in

th[at] case.” Ibid.

The Second Circuit also addressed this issue in a Connecticut case where

a family died in a tragic house fire resulting from suspected arson. United

States v. Natal, 849 F.3d 530, 532-33 (2d Cir. 2017). The defense sought to

present a theory that the home’s landlord was a plausible suspect in the arson.

Id. at 534. To rebut this, the government sought to introduce testimony from a

Sprint Nextel employee that on the night of the fire, the landlord’s cell phone

connected to cell towers in New York City and not in New Haven,

Connecticut. Ibid. The government did not seek to qualify the witness as an

expert under Fed. R. Evid. 702 but called him to testify as a records custodian.

Id. at 534-35. The trial court admitted the testimony over the defendants’

objection. Id. at 535. The Second Circuit concluded that admission of this

testimony was improper and held that “testimony on how cell phone towers

operate must be offered by an expert witness.” Id. at 536 (joining the Seventh

and Tenth Circuits in this holding). The court further noted that “the line

between testimony on how cell phone towers operate, which must be offered

by an expert witness, and any other testimony on cell phone towers, will

frequently be difficult to draw, and so both litigants and district courts would

39

be well advised to consider seriously the potential need for expert testimony.”

Ibid.

IV.

Applying those principles, we hold that Detective Leyman’s testimony

regarding CSLI was improperly admitted as lay opinion testimony. The CSLI

testimony should have been presented by a witness qualified as an expert

pursuant to N.J.R.E. 702 because the technical aspects of CSLI are beyond the

ken of the average juror.

Before the start of trial, the court attempted to draw a line between CSLI

testimony that simply presented tower location information and testimony

about the technical aspects of how cell towers operate. But as the Second

Circuit has cautioned, “the line between testimony on how cell phone towers

operate, which must be offered by an expert witness, and any other testimony

on cell phone towers, will frequently be difficult to draw.” Natal, 849 F.3d at

536. This principle became evident in the trial court’s many limiting

instructions to the jury.

The trial court ordered that Detective Leyman could provide only “lay

witness testimony regarding his review, interpretation, and plotting of cell

towers on a map from defendant’s historical cell site data records.” The court

prohibited lay witness testimony about the direction in which cell towers

40

transmit and receive calls. Additionally, the court barred testimony about calls

that were connected to one cell tower at the start of the call but to a different

tower at the end of the call. Then, through a series of instructions, the trial

court thoughtfully attempted to clarify how and for what purpose the jury

could consider the CSLI evidence. The court’s repeated attempts to instruct

the jury regarding CSLI illustrate the complexity of that testimony and

demonstrate exactly why such evidence must be presented by an expert

witness.

At trial, the jury first heard about CSLI through a series of questions

posed by the prosecutor. Through his responses, Detective Leyman asserted

that CSLI can reveal where a person was located at a particular time.

Specifically, when asked whether “those phone records [would] have provided

information regarding where [the suspect] may have been located at the time

that the homicide occurred?,” Detective Leyman answered, “[y]es.” That is

exactly the testimony -- precise location information -- the trial court ordered

could not be presented to the jury.

Detective Leyman then testified about defendant’s cell site location

records, explaining how he plotted the locations of each cell tower that

defendant’s cell phone connected to during the relevant time period.

Throughout his testimony, Detective Leyman associated the cell towers to

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which defendant’s cell phone connected with the path the victim traveled the

morning of his death. After the start of Detective Leyman’s testimony, the

trial judge gave a limiting instruction to the jury that they should not consider

the evidence to mean that the cell phone was “there or here or any other

particular place” -- instructions that completely contradicted Detective

Leyman’s testimony that the phone records could help identify a person’s

location. Detective Leyman’s testimony, in combination with the attempted

curative instructions, had the potential to confuse and mislead the jury absent

an expert witness’s testimony to clarify the import -- and limitations -- of the

CSLI evidence.

Furthermore, although the trial court tried to clarify the permissible use

of cell site evidence for the jury through multiple limiting instructions, those

efforts were potentially undone by the prosecutor’s comments in summation.

After the trial court advised the jury multiple times that the cell tower evidence

they heard does not indicate where a cell phone was located, the prosecutor

told the jury that a “phone has to be close to the tower that’s being accessed.

I’d say a stone’s throw.” The prosecutor also stated that the records showed

defendant’s “phone . . . clearly moving with the victim because it’s hitting off

of towers [in] the same direction that the victim is traveling.” Those

comments in summation, particularly the prosecutor’s statement that the phone

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must be a stone’s throw away from the tower, essentially told the jury that a

cell phone must be fairly close to a cell tower to connect. Throughout its three

limiting instructions, the trial court repeatedly told the jury that the cell tower

data does not provide location information: “[T]he fact that there was a phone

call received at that tower does not mean that phone was in any particular

location”; “the location of any particular phone at any particular time is . . . an

independent question of fact that you must decide for yourself”; “That cell

tower doesn’t tell you that phone was there or there. It tells you the phone

connected that cell tower.” So the State’s comments in summation directly

contravened the trial court’s instruction to the jury about what they could infer

from the CSLI testimony absent other corroborating evidence.

Additionally, the trial court’s final jury charge was not clear enough to

neutralize any confusion caused by the prosecutor’s closing remarks. In

response to defense counsel’s objection, the trial court instructed the jurors

that they could not “conclude that a phone was in any particular spot simply

because it connected to a tower.” But the court then added, “[y]ou can,

however, utilize that information along with other information if you think it’s

appropriate to do so.” The mixed messages to the jury regarding the

significance of CSLI should have been clarified by the testimony of an expert

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witness, which would have also made it possible to provide adequate

instructions to the jury about the permitted use of CSLI.

CSLI, by definition, is not exact. Exact location information must

instead be obtained via GPS -- information an expert witness could have

explained to the jury. But CSLI does provide information on a cell phone’s

general location. For a phone to connect to a particular cell phone tower, that

phone must be within that tower’s coverage range, whatever that radius might

be. See Beck, 49 Crim. L. Bull. at 645.

Indeed, the only purpose for presenting CSLI at trial is to provide the

jury with evidence about the general location of a pertinent cell phone at a

particular time. That is what makes CSLI admissible as relevant evidence

under N.J.R.E. 401. The fact that CSLI can tend to show that a phone was in a

particular general area during a time period relevant to the case is the very

reason the State presented such evidence in the first instance. There is no

logical purpose to allow CSLI testimony only to then tell the jury that they are

not permitted to use the evidence to determine the location of a phone. A jury,

properly informed about the intricacies and nuances of cell towers, should be

able to use CSLI to place a phone in a general area. But that cannot happen if

a jury is not properly equipped with the tools necessary to understand this

relevant evidence.

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Further, leaving the jury to draw any inferences it deemed appropriate

from the non-contextualized CSLI evidence -- without a full explanation of its

technical aspects and capabilities by an expert witness -- also risked confusing

and misleading the jury in violation of N.J.R.E. 403. The State argued that any

layperson, including members of the jury, can determine and plot locations of

cell towers by using the towers’ longitude and latitude provided in the records

and inputting those numbers into an internet mapping application. Although a

jury may be able to figure out the location of cell towers using phone records,

it would not be able to draw any meaningful inferences from that information

without an understanding of how cell towers operate and why those cell tower

locations matter. And, in the absence of expert guidance, a jury could attribute

more or less weight to the tower locations than is warranted.

As noted, many jurisdictions allow witnesses to provide limited

testimony about the locations of cell phone towers that cell phones connect to

without the testifying witness being qualified as an expert. We disagree with

that approach. The relevance of CSLI can be understood by a jury only when

it has a better grasp of how cell towers and cell phones interact. This requires

an understanding of cell tower sectors, direction, and maximum coverage

range, and the many factors, such as terrain and topography, that impact

whether a cell phone connects to the closest tower or to one that is farther

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away. The technical and specialized knowledge required to interpret CSLI is

beyond the ken of the average juror. Therefore, CSLI evidence must be

presented by an expert witness.

Testimony that simply communicates the cell tower locations to the jury

without an expert witness explaining the significance of those locations is

similar to the brake pad and brake fluid testimony in Wyatt, 217 N.J. Super. at

591-92, and the lay testimony regarding airbag deployment in Taing, 454 N.J.

Super. at 469-71. The Wyatt and Taing courts required expert witnesses to

connect those facts to the issues of consequence in those cases. In this case,

merely providing cell tower locations -- without any information about the

range of those towers or how the towers technologically interact with cell

phones -- did not help the jury understand where defendant’s phone was

potentially located during the relevant time period. More troubling still, the

limited CSLI evidence presented violated the trial court’s order and led to

improper arguments in summation by the State. N.J.R.E. 403 requires

exclusion of such testimony, which could lead a jury to make impermissible

inferences, resulting in confusion.

Finally, the CSLI testimony that the jury heard in this case, in the form

of testimony and the State’s closing argument, is at odds with our holding in

Burney. In that case, we held that an FBI special agent’s testimony regarding

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the range of a particular cell tower was an impermissible net opinion because it

was based on nothing more than the agent’s own “rule of thumb” and not on

scientific or technical data. 255 N.J. at 5, 25. Here, Detective Leyman told

the jury that phone records indicated where a person may have been located at

the time of Lopez’s death -- a conclusion that Detective Leyman did not

support with technical data. In summation, the State then relied on Detective

Leyman’s testimony to assert that a phone must be “a stone’s throw” from the

tower it connects to, and thus that defendant’s phone was “clearly moving”

with the victim. If an expert attempted to offer the same conclusory

information that Detective Leyman did, that expert’s testimony would

constitute an impermissible net opinion in violation of N.J.R.E. 703 because

the conclusions were unsupported by adequate data. The State cannot

circumvent the standards to which expert testimony is held under N.J.R.E. 702

by presenting the testimony through a lay witness rather than an expert.

As gatekeepers of the evidence, trial courts must ensure that relevant

evidence properly goes before the jury in a manner that assists the jury. In

order to understand CSLI, which is beyond the ken of the average juror, an

expert witness must be called to testify. Here, admission -- over repeated

objections -- of the CSLI testimony was a clear error, see Garcia, 245 N.J. at

430, that was not cured by the limiting instructions given.

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V.

For the foregoing reasons, we affirm the Appellate Division’s judgment.

CHIEF JUSTICE RABNER and JUSTICES PATTERSON, WAINER

APTER, FASCIALE, NORIEGA, and HOFFMAN join in JUSTICE PIERRE-

LOUIS’s opinion.

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