by David Kim

The Supreme Court of New Jersey unanimously held that historical cell site location information (“CSLI”) may not be presented to a jury through a lay witness. Instead, because CSLI carries probative force only when the jury understands how cell towers and cellphones interact, the Court ruled that such evidence involves “technical and specialized knowledge” that must be introduced through a witness qualified under N.J.R.E. 702.

Background

Jule Hannah’s homicide prosecution arose from the January 15, 2017, shooting death of Miguel Lopez, who was found in the driver’s seat of a crashed Chrysler Sebring on Spruce Street in Bridgeton. The State’s theory was that Lopez picked defendant up in Monroe Township shortly after defendant reported a one-car accident there around 7:27 a.m. and that defendant then rode with Lopez toward Bridgeton before shooting him from the passenger side.

The State’s proof was circumstantial. Investigators recovered a cigar butt from the front passenger seat, and a forensic scientist testified that the cigar butt contained DNA from a single source matching defendant. The State also introduced evidence of a recorded call during the relevant period in which a third person could be heard in addition to Lopez and the caller. But the State’s effort to place defendant with Lopez during the drive depended heavily on defendant’s cell phone records and the locations of the towers his phone connected to.

Before trial, the State sought to qualify Detective Leyman as an expert in historical cell site analysis. Leyman testified that he had reviewed cell phone records in dozens of cases, had taken a “high tech investigation” course covering phone records, had learned from carrier personnel how to interpret such records, and had military training in mapping and directional navigation. The State acknowledged at the hearing that it needed expert qualification “in order for this testimony to come in.” However, after defense counsel challenged Leyman’s qualifications, the trial court drew a narrower line. It allowed Leyman to testify as a lay witness about tower locations and the times calls connected to them but barred testimony about antenna azimuths, tower sectors, and “the location of any phone at any particular time.”

That compromise was not adhered to at trial. Leyman told the jury that the records could provide information about where a suspect “may have been located” at the time of the homicide, walked the jury through Sprint call detail records, and plotted the locations of towers defendant’s phone connected to during the critical period. The State then used those records to compare tower locations with the route Lopez traveled and the location of defendant’s crash. Although the trial court repeatedly instructed the jury that cell-tower evidence did not itself establish where a phone was located and did not alone prove a phone moved, the State’s summation pushed the inference further, telling jurors that a phone has to be close to the tower it accesses, “a stone’s throw” away, and arguing that defendant’s phone was “clearly moving” with the victim.

After conviction, the Appellate Division reversed, holding that historical CSLI could not be introduced through lay testimony. The New Jersey Supreme Court granted the State’s petition for certification.

Analysis

The Court began its analysis by reviewing the line between lay and expert testimony. Under N.J.R.E. 701, a non-expert witness may offer an opinion only if it is rationally based on the witness’ perception and will assist the factfinder. Lay opinion has limits. It does not permit testimony on matters outside the witness’ “direct ken” and on which the jury is as competent as the witness to draw a conclusion. State v. Sanchez, 255 A.3d 1118 (N.J. 2021). When the subject is beyond “common knowledge and observation,” N.J.R.E. 702 governs instead. The Court noted that expert testimony is required when the issue is “so esoteric” that jurors of ordinary judgment and experience cannot form a valid conclusion without assistance. Hopkins v. Fox & Lazo Realtors, 625 A.2d 1110 (N.J. 1993). And even expert testimony must rest on supporting facts or data; otherwise it is inadmissible as a net opinion. Townsend v. Pierre, 110 A.3d 52 (N.J. 2015); Pomerantz Paper Corp. v. New Cmty. Corp., 25 A.3d 221 (N.J. 2011).

The Court then explained why CSLI falls on the expert side of that divide. A cellphone generally connects to the cell site with the strongest signal, but signal strength does not turn on proximity alone. United States v. Hill, 818 F.3d 289 (7th Cir. 2016). It is also affected by tower characteristics, geography and topography, the angle and number of antennas, features of the phone itself, and other environmental factors. State v. Earls, 70 A.3d 630 (N.J. 2013). For that reason, CSLI is inherently limited. The Court noted that unlike GPS, it does not provide exact location data; at most, it can help identify a phone’s general location within a tower’s coverage range. State v. Burney, 298 A.3d 1080 (N.J. 2023); In re Application for Ord. Authorizing Pen Register, 415 F. Supp. 2d 211 (W.D.N.Y. 2006). The Court explained that CSLI is relevant because it may help place a phone in a general area at a relevant time, but that inference is meaningful only if the jury understands the technical premises and limitations that give the data weight.

Turning to the case law, the Court acknowledged that many jurisdictions have permitted limited lay testimony about the locations of towers listed in call records, even while requiring expert testimony for more technical opinions about how towers operate or why a phone connected to a particular site. See, e.g., United States v. Graham, 796 F.3d 332 (4th Cir. 2015); State v. Boothby, 951 N.W.2d 859 (Iowa 2020); State v. Sinnard, 543 P.3d 525 (Kan. 2024); Torrence v. Commonwealth, 603 S.W.3d 214 (Ky. 2020); State v. Blurton, 484 S.W.3d 758 (Mo. 2016); Burnside v. State, 352 P.3d 627 (Nev. 2015); State v. Wyman, 107 A.3d 641 (Me. 2015). Nevertheless, the Court favored Maryland’s more demanding approach. In State v. Payne, 104 A.3d 142 (Md. 2014), the Court of Appeals of Maryland (now known as the Supreme Court of Maryland) rejected the premise that a layperson armed with call records and instructions could determine the pertinent tower locations without specialized knowledge, reasoning that call detail records contain technical data unfamiliar to ordinary jurors and that the process of identifying which entries matter and how to interpret them is itself “beyond the ken of an average person.” The Court also relied on the Second Circuit’s warning that the line between testimony about how towers operate and other tower-related testimony is often difficult to draw, making expert testimony the sounder course. United States v. Natal, 849 F.3d 530 (2d Cir. 2017).

The Court then applied those principles to the trial record and concluded that the very course of the defendant’s trial demonstrated why expert testimony was required. The trial court tried to carve out a lay-only subset of CSLI testimony by allowing Leyman to identify and plot tower locations while barring opinions about direction, sectors, switching, and the location of a phone “at any particular time.” But the Court determined that line was impossible to maintain in practice. Leyman’s testimony that the records could show where a suspect “may have been located” crossed directly into location testimony the trial court had purported to exclude. His walkthrough of defendant’s call records and plotted towers then associated those towers with Lopez’s route and with the location of defendant’s crash. The Court explained that those inferences were important because the central disputed issue was whether defendant was in Lopez’s car before the killing, and the State used the cell-tower evidence to support that theory.

The Court next explained that the trial court’s repeated limiting instructions did not solve the problem; they illustrated it. A proper limiting instruction can sometimes cure juror confusion, but incomplete or contradictory instructions can also compound prejudice. Hrymoc v. Ethicon, 297 A.3d 1245 (N.J. 2023); State v. Sanchez-Medina, 176 A.3d 788 (N.J. 2018).

In the present case, the instructions repeatedly told the jury that tower evidence did not establish where a phone was and did not, by itself, prove movement. However, Leyman’s testimony and the State’s questioning encouraged the jury to use tower locations for exactly that purpose, according to the Court. The prosecutor’s summation then sharpened the contradiction by telling jurors that common experience shows a phone must be close to the tower it connects to, that “a stone’s throw” was a fair description, and that defendant’s phone was “clearly moving” with the victim. In the Court’s view, those comments effectively supplied a technical premise, proximity to the strongest tower, without expert support, while also undermining the trial court’s own instructions about what the jury could infer from the evidence.

The Court stated that the difficulty was not merely procedural. It went to both relevance and the risk of misuse. CSLI is relevant because it may tend to show that a phone was in a particular general area during a relevant period. N.J.R.E. 401. But if a jury is given raw or partially interpreted tower data without the technical explanation needed to understand range, sectors, direction, tower selection, and the reasons a phone may connect to a more distant site, that same evidence risks confusing or misleading the jury, the Court reasoned. N.J.R.E. 403. A jury might know how to enter latitude and longitude into a mapping program and locate towers on a map, but it cannot draw meaningful inferences from those locations without understanding how cell towers operate and why those locations matter. That is why the Court rejected the approach of jurisdictions allowing limited lay testimony about tower locations alone. Thus, the Court held that the technical and specialized knowledge required to interpret CSLI is beyond the ken of the average juror, so the evidence must come through an expert witness.

The Court also based its holding on Burney. In that case, the state Supreme Court barred expert CSLI testimony that rested only on an FBI agent’s unsupported “rule of thumb” about tower range. In the present case, the trial presented the same issue. Leyman told the jury that the phone records indicated where a person may have been located, and the State converted that testimony into the claim that defendant’s phone must have been near the accessed towers and moving with Lopez. The Court explained that had an expert offered those same conclusions without supporting technical data, the testimony would have been an inadmissible net opinion under N.J.R.E. 703. The State cannot evade the standards that govern expert testimony under N.J.R.E. 702 by presenting the same unsupported conclusions through a lay witness instead, the Court concluded.

Conclusion

The Court held that historical CSLI involves “technical and specialized knowledge” that must be presented through expert testimony under N.J.R.E. 702, not through lay testimony under N.J.R.E. 701. Although CSLI can help place a phone in a general area, its meaning depends on technical features and limitations that are beyond the ken of the average juror, and presenting tower-location evidence without that context risks confusion and misleading inferences under N.J.R.E. 403. Leyman’s testimony crossed into unsupported location inferences, the State’s closing argument amplified those inferences, and the limiting instructions did not cure the resulting prejudice.

Accordingly, the Court affirmed the Appellate Division’s order reversing the defendant’s conviction and remanding for a new trial. See: State v. Hannah, 2026 N.J. LEXIS 378 (2026).

Editor’s Note: Anyone with an interest in CSLI is encouraged to read the Court’s full opinion.

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