DISTRICT COURT OF APPEAL OF THE STATE OF FLORIDA

FOURTH DISTRICT

J.A.R., a child,

Appellant,

v.

STATE OF FLORIDA,

Appellee.

No. 4D2022-2469 

[November 8, 2023]

Appeal from the Circuit Court for the Fifteenth Judicial Circuit, Palm 

Beach County; Lisa S. Small, Judge; L.T. Case No. 502021CJ001093AMB.

Carey Haughwout, Public Defender, and Nancy Jack, Assistant Public 

Defender, West Palm Beach, for appellant.

Ashley Moody, Attorney General, Tallahassee, and Sorraya M. SolagesJones, Assistant Attorney General, West Palm Beach, for appellee.

LEVINE, J.

Appellant appeals the order which withheld an adjudication of 

delinquency for unlicensed carrying of a concealed firearm and possession 

of a firearm by a minor. Appellant argues that the trial court erred when 

it admitted an expert’s testimony regarding “ShotSpotter” technology, 

which can detect the sound of gunfire and notify police. Appellant claims 

the state failed to present substantial competent evidence that the expert’s 

scientific testimony was reliable. We find that the trial court did not err in 

admitting the testimony under Daubert and section 90.702. As to the 

other issues raised by appellant, we affirm without further comment.

On September 14, 2021, at 12:43 a.m., a gunshot detection system 

known as ShotSpotter alerted to a shot fired at an address in Riviera 

Beach. Using real time surveillance cameras, an officer observed two 

males—one of whom was appellant—walking from the immediate area of 

the alert. No other individuals were in the area. Another officer 

immediately responded to the scene and made contact with the two 

individuals. The officer observed bulges in appellant’s pockets, which he 

believed to be a firearm. The officer asked the individuals if they heard 
2

any gunshots, and appellant stated he did. The officer asked if he could 

check them for weapons, and they both agreed. The officer found a firearm 

and magazine inside appellant’s pockets. 

Appellant was charged with unlicensed carrying of a concealed firearm 

and possession of a firearm by a minor. The ShotSpotter evidence was 

used at trial, in part to explain why police responded to the location and 

why they made contact with appellant. 

Before the bench trial, appellant moved to exclude expert testimony 

regarding ShotSpotter technology as it relates to detecting gunfire, arguing 

the testimony was inadmissible under section 90.702 and Daubert. The 

state responded that the testimony satisfied section 90.702 and Daubert. 

During a hearing on the motion to exclude, the court heard testimony 

from the expert, Collier, a forensic services manager at ShotSpotter, Inc., 

with seven years of experience. Collier had previously testified over 70

times about the ShotSpotter system and had been qualified as an expert 

on most occasions. He explained that ShotSpotter is an acoustic gunshot 

detection and location system, which uses GPS enabled microphones and 

sensors to geolocate detected gunfire. The ShotSpotter system has three 

components: sensors, a location server, and an application. The sensors 

receive impulse data, which they pass to the location server, which in turn 

processes that data to determine the location. That information is then 

passed on to a person who reviews the system’s findings and provides a 

classification. At that point, the information is published to an application 

that runs on an iPad, iPhone, office computer, or mobile data computer. 

Collier stated that ShotSpotter technology is primarily based on two 

techniques. The first technique is the “time difference of arrival,” which 

measures the time difference that an “impulsive sound” arrives at one or 

more sensors. Time difference of arrival is a concept that when sensors 

are pinged or capture an impulsive sound, there are different distances 

from that impulse. The process of determining where that sound occurred 

is measuring that time difference of arrival. The difference in time of 

arrival at two points can be plotted onto a map or graph paper. 

The second technique is “multilateration,” which makes use of the time 

difference of arrival at three or more listening locations to determine where 

the sound originated. It can be illustrated by hyperbolic curves between 

the locations that eventually intersect. Multilateration is used in avionics 

to determine the location of aircrafts and airports. Its early uses date back 

to World War I, when multilateration was used to determine where to 

return artillery fire. 
3

Collier testified that ShotSpotter is able to accurately determine the 

location of gunfire within a 25-meter radius, which is the length of a 

basketball court. An independent audit, using data from 2019 and 2020, 

confirmed ShotSpotter had an accuracy rate of 97%, with an error rate of 

.41%, which ShotSpotter rounded up to .5%. 

Collier testified in more detail as to each of the components of the 

ShotSpotter system. A program manager and project team determine the 

optimum placement and number of sensors to be installed. A sensor has 

the following primary components: a microphone, a CPU that processes 

data and stores audio information, a GPS receiver to know where the 

sensor is located and to receive time synchronization, and a means of 

connecting to the internet via a cellular radio. 

The sensors listen for impulsive sounds, such as a clap, a dog barking, 

or jackhammers. If at least three sensors capture a series of impulsive 

sounds, the information is passed on to the location server. The location 

server runs algorithms that include techniques like multilateration to 

determine whether the sound is likely gunfire and whether the location 

can be determined with a high degree of confidence. If the answers to 

these inquiries are yes, the location and audio clips are passed on to a 

reviewer who determines whether the sound is gunfire. 

Collier noted that ShotSpotter has two incident review centers. Each 

review is performed within 60 seconds of receipt. The employees who 

review the impulsive sounds are trained to determine whether the audio is 

gunfire. They consider how far the sound traveled and listen for context 

clues, such as tires screeching. If the reviewer believes there is gunfire, 

then the information is published. A published incident goes to user 

interface, like an iPhone or iPad, where the user receives an alert to view 

the incident on the map and play the audio. 

Clocks on the sensors are synchronized through GPS receivers to 

satellite time that is accurate to the millisecond. The system is regularly 

checked on three levels to confirm it is working. First, each sensor sends 

a signal every minute or so to the location server to confirm it is operating. 

Second, third party applications that run on the system check to see if a 

sensor is available. Third, the customer support team routinely confirms 

the sensors are operating.

 

Collier testified that the ShotSpotter system is installed in over 100 

cities and has been around over 20 years. He further stated that the 

company does not release to the public the location of the sensors or what 
4

the sensors look like for safety reasons, because some are installed on 

private residences, and to prevent intentional destruction or damage of the 

devices. The two techniques ShotSpotter relies on—multilateration and 

time difference of arrival—have been tested and peer reviewed and are 

generally accepted in the scientific community. 

Collier performed a post-analysis review to confirm the time, location, 

and account of this shooting incident and documented his findings in a 

detailed forensic report. Collier testified in detail regarding his forensic 

report, which was introduced into evidence. Four sensors were used to 

identify a single gunshot fired at 12:43 a.m. on September 14, 2021, at an 

address in Riviera Beach. Although only three sensors were needed, the 

fourth sensor confirmed the findings of the other three. The 

multilateration process was used to determine the coordinates and to 

provide the address to the police. 

The trial court denied the motion to exclude, finding that Collier 

qualified as an expert in ShotSpotter technology. The trial court further 

found his expert opinion was admissible under Daubert’s three prongs. 

First, Collier’s testimony was based on sufficient facts and data. Collier 

went through his report in detail, explaining the facts and data upon which 

he relied. Second, ShotSpotter’s technology was based upon tested and 

accepted principles in the scientific community, that being multilateration 

and time difference of arrival. The trial court further found that the 

technology had been tested by a third party, albeit commissioned by 

ShotSpotter.1 ShotSpotter had its own internal checks, such as three 

levels of ensuring the sensors are working. Third, Collier applied the 

principles and methods reliably to the facts of the case. He explained what 

data he used and how he applied the multilateration and time difference 

of arrival principles. Based on these findings, the trial court overruled 

appellant’s Daubert challenge. 

After a bench trial, the trial court withheld adjudication of delinquency 

for unlicensed carrying of a concealed firearm and possession of a firearm 

by a minor. This appeal follows. 

Appellant argues that the trial court erred in admitting the expert 

testimony about the ShotSpotter technology alert for gunfire, claiming that 

the expert’s testimony failed to show the technology was scientifically 

reliable. Further, appellant claims that the trial court failed to perform its 

1 The trial court noted the error rate was determined to be .15%, but Collier 

actually testified to an error rate of .5%, which he explained was rounded up from 

.41%. 
5

gatekeeping function under Daubert. The state, in turn, argues that the 

trial court did not abuse its discretion in admitting the expert testimony 

of the ShotSpotter technology and that the expert’s testimony satisfied 

Daubert and section 90.702.

A trial court’s ruling on the admissibility of expert testimony under 

section 90.702, Florida Statutes (2021), is reviewed under the abuse of 

discretion standard. Kemp v. State, 280 So. 3d 81, 88 (Fla. 4th DCA 2019).

Section 90.702 codifies the Daubert standard as follows:

If scientific, technical, or other specialized knowledge will 

assist the trier of fact in understanding the evidence or in 

determining a fact in issue, a witness qualified as an expert 

by knowledge, skill, experience, training, or education may 

testify about it in the form of an opinion or otherwise, if:

(1) The testimony is based upon sufficient facts or data;

(2) The testimony is the product of reliable principles and 

methods; and

(3) The witness has applied the principles and methods 

reliably to the facts of the case.

A trial judge, under Daubert, has a gatekeeping role in order to “ensure 

that any and all scientific testimony or evidence admitted is not only 

relevant, but reliable.” Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 

U.S. 579, 589 (1993). When exercising the gatekeeping function, the trial 

judge makes “a preliminary assessment of whether the reasoning or 

methodology underlying the testimony is scientifically valid and of whether 

that reasoning or methodology properly can be applied to the facts in 

issue.” Id. at 592-93. 

Some of the relevant factors to be considered when determining the 

reliability of expert testimony include the following: (1) whether the theory 

or technique can be and has been tested, (2) whether the theory or 

technique has been subjected to peer review and publication, (3) the 

known or potential rate of error and the existence and maintenance of 

standards controlling the technique’s operation, and (4) the general 

acceptance in the scientific community. Id. at 593-94. However, it is also 

important to note the test of reliability is flexible, and the list of Daubert

factors do not apply to all experts or in every case. Kumho Tire Co. v. 

Carmichael, 526 U.S. 137, 141 (1999).
6

We find that the trial court did not abuse its discretion in admitting 

Collier’s testimony regarding the ShotSpotter technology. Collier had 

seven years’ experience working at ShotSpotter, including working as a 

forensic services manager performing forensic reviews of the technology’s 

data and documents. Further, Collier had previously testified over 70 

times about the ShotSpotter system and had been qualified as an expert 

on most occasions. Based on all this background, Collier had been 

“qualified as an expert by knowledge, skill, experience, training, or 

education.” § 90.702, Fla. Stat. (2021). 

We also find that Collier’s testimony satisfied all three prongs of 

Daubert. First, Collier’s testimony was based upon more than sufficient 

facts or data. The testimony included details about the ShotSpotter 

system’s sensors, location server, and application. Collier testified how 

the location of the gunfire was determined by multilateration, which makes 

use of the time difference of arrival, at three or more listening locations, to 

determine where the sound originated. Finally, Collier, in the hearing,

went step-by-step over his detailed forensic report.

Second, Collier’s testimony was the product of reliable principles and 

methods. Collier testified that the ShotSpotter technology is based on two 

different techniques: multilateration and time difference of arrival. He 

explained how these techniques worked to locate a sound. Collier testified 

that these techniques have been used since World War I and are still used 

in avionics. Specifically, the ShotSpotter system has been installed in over 

100 cities and has been in existence for around 20 years. Collier stated 

that ShotSpotter is able to accurately determine the location of gunfire 

within a 25-meter radius. An external audit confirmed that this system 

had an error rate of less than half a percent. Finally, ShotSpotter has 

three levels of internal checks to ensure sensors are working. 

Third, Collier applied the principles and methods reliably to the facts of 

this case. Collier explained the data he used and how he applied the 

multilateration and time difference of arrival principles. In this case, four 

sensors were used, even though multilateration requires only three 

sensors, and the fourth sensor confirmed the findings of the other required 

three sensors.

Appellant argues that the prongs of Daubert were not met. We disagree. 

Trial judges “have considerable leeway in deciding in a particular case how 

to go about determining whether particular expert testimony is reliable.” 

Carmichael, 526 U.S. at 152. All of appellant’s arguments go to the weight 

of the evidence, rather than to its admissibility. Appellant objects, for 
7

example, to Collier’s testimony because he is not an engineer. However, 

an “expert is not required to have an in-depth knowledge of all the 

algorithms underlying their technological tools—such as hardware and 

software—to reliably testify about the outputs of those tools.” Walker v. 

State, 308 So. 3d 193, 198 (Fla. 4th DCA 2020) (citation and internal 

quotation marks omitted). Thus, Collier could testify to the “outputs” of 

the tools, that being the determination of the location of gunfire. 

Finally, we also note that other jurisdictions have determined that 

ShotSpotter technology is reliable and consequently have denied pretrial 

motions in limine. See State v. Hill, 851 N.W.2d 670, 689-91 (Neb. 2014)

(rejecting argument that ShotSpotter technology was not reliable under 

Daubert and affirming denial of pretrial motion in limine); People v. Brewer, 

F082631, 2023 WL 3447037, at *12-13 (Cal. Ct. App. May 15, 2023), 

review granted (July 26, 2023) (holding the same); see also Leila Lawlor, 

Hardware, Heartware, or Nightmare: Smart-City Technology and the 

Concomitant Erosion of Privacy, 3 J. Comp. Urb. L. & Pol’y 207, 220 (2019)

(“ShotSpotter recordings and reports are regularly admitted into 

evidence.”). 

In summary, we find that the trial court did not err or abuse its 

discretion in admitting the testimony regarding the ShotSpotter 

technology and determining that it met the Daubert test. As such, we 

affirm.

Affirmed. 

GERBER and CONNER, JJ., concur.

* * *

Not final until disposition of timely filed motion for rehearing.