### D ISTRICT 

### C OURT 

### O F 

### A PPEAL 

### O F 

### T HE 

### S TATE 

### O F 

### F LORIDA

F OURTH D ISTRICT

J

. A

. R

. , a child

, Appellant,

v.

STATE OF FLORIDA
, Appellee

.

No. 4D 20 22

- 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. Solages

Jones, Assistant Attor ney General, West Palm Beach, for appellee.

L EVINE
, J.

Appellant appeals the order which withheld a n adjudication of delinquency for unlicensed carrying of a concealed firearm and possession of a firearm by a minor. Appellant argues that the trial cour t 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.

O n September 14, 2021

, at 12:43 a.m., a gunshot detection system known as ShotSpotter alerted t o a shot fired at an address in Riviera

Beach. Using real time surveillance camera s, an officer observed two
males

— one of whom was appellant

— walking from the immediate area of

the al ert. No other individuals were in the area. An other 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 indiv iduals if they heard2 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 carr ying 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 b een 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: s ensors, 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 finding s 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 technique s. 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, t here are differen t 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 interse ct. Multilateration is used in avionics to determine the location of aircrafts and airports. Its early uses date back

to W orld W ar 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 followin g 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 sensor s 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 det ermines 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 m ap 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 ever y 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 sensor s are operating.

Collier tes tified that t he 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 what4 the sensors look like for safety reasons, because s ome are installed on private residences, and to prevent intentional destruction or damage of the

devi c es. 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

rep ort, which was introduced into evidence. Four sensors were used to identify a single gunshot fired at 12:4 3 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 t he 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 t he technology had been tested by a third party, albeit comm issioned 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 o f 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 Shot S potter technology alert f o r gunfire, claiming that the expert’s testimony failed to show the technology was scientifically

reliable. Further

, appellant claim s 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 Shot S potter 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 u nder the abuse of

discretion standard. Kemp v. State , 280 So. 3d 81, 88 (Fla. 4 th 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 suffici ent 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 “ensur e 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 asses sment of whether the reasoning or methodology underlying the testimony is scientifically valid and of whether

th at reasoning or methodology properly can be applied to the facts in

issue.” Id

. at 592

- 93.

Some of the r elevant factors to be considered whe n 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 Shot S potter te chnology. 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 S hot S potter 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 Co llier’s testimony satisfied all three prongs of

Daubert

. First, Collier’s testimony was based upon more than sufficient facts or data. The testimony included detail s about the Shot S potter system’s sensors, location server

, and application. Collier testi fied 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 o ver his detailed forensic report.

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

methods. Collier testified that the Shot S potter 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 Shot S potter system has been installed in over

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

that Shot S potter 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. Fina lly, Shot S potter 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 Dauber t 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 weigh t of the evidence, rather than to its admissibility. A ppellant objects , for7 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 technologi cal 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 t ools, that being the determination of the location of gunfire.

Finally, we also note that other jurisdictions have determined that

Shot S potter technology is reliable and consequently have denied pretrial

motions in limine. Se e State v. Hill , 851 N.W.2d 670, 68 9

- 9 1 (Neb. 2014) (rejecting argument that ShotSpotter technology was not reliable under

Daubert and affirming denial of pret rial 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

Concomita nt 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 rega rding the Shot S potter technology and determining that it met the Daubert test. As such, we

affirm.

Affirmed

.

G ERBER and C ONNER
, JJ., concur.

* * *

Not final until disposition of timely filed motion for rehearing.