Faustin v. State · Nos. 4D2024-2667 and 4D2024-2669 (Fla. 4th DCA) · Decided October 7, 2026
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A man convicted in Broward County of two counts of vehicular homicide will get a new trial because a detective who was not an accredited accident reconstructionist was allowed to estimate the vehicles’ speeds using a “momentum formula” without the expert-testimony analysis section 90.702, Florida Statutes, requires, the Fourth District Court of Appeal has held. The court found the error was not harmless, even though the vehicles’ event data recorders also supplied speed information.
What Happened
Neckson Faustin was convicted of two counts of vehicular homicide and one count of reckless driving causing property damage. In a related case, the trial court revoked his probation and imposed sentence. The two appeals were consolidated.
At trial, Detective Michael Wiley, a lay witness who acknowledged he was not an accredited accident reconstructionist, testified to the speeds of the vehicles involved in the crash based on a calculation using what he called a “momentum formula.” The trial court allowed the testimony on the theory that Wiley was merely testifying about his investigation.
According to the opinion, Wiley used vehicle weights derived from averages found through internet searches, without accounting for differences between trim levels and vehicle styles. He calculated departure angles using Google Maps and a protractor, although he acknowledged those angles must be “very accurate.” He assumed the Corolla’s approach angle was zero because “[t]hat is how we are taught to do it when we use this formula.” And he could no longer produce the field sketch documenting how he reached his calculations.
The defense expert, Aaron Moss, an accredited accident reconstructionist, testified that Wiley’s unscaled field sketch was insufficient to calculate speed, that the video was too unclear to support the assumption that the Corolla was traveling straight at impact and the event data recorder indicated otherwise, that he had never encountered averaged internet-sourced vehicle weights in a momentum calculation, and that Wiley used the wrong trim level for the Corolla.
What the Court Held
The State did not defend the ruling on the merits. The court wrote that “[t]he state essentially concedes error, as it does not address the merits of the defendant’s argument and instead argues any error was harmless.”
The court nonetheless explained why the testimony was improper. Wiley “opined as to the vehicles’ speeds based on a formula which he apparently learned during his training,” and “[t]his is not permissible lay opinion testimony,” the court wrote, citing section 90.701. “Because Wiley’s calculation depended on specialized knowledge and methodology, it constituted expert opinion testimony subject to section 90.702.” The trial court did not conduct the assessment that section, which “codifies the Daubert standard,” requires.
The court did not decide whether momentum analysis is itself reliable. “Even assuming that momentum analysis may constitute a reliable methodology when properly performed,” it wrote, the State did not establish that Wiley’s opinion rested on sufficient case-specific facts or data or that he reliably applied the methodology to this collision.
On harmless error, the State argued the event data recorders supplied speed information. But testimony established that the data could not be reliably interpreted without independent accident reconstruction, so Wiley’s calculations “did not merely duplicate the event-data-recorder evidence.” They “purported to corroborate that evidence on an issue central to whether the defendant drove recklessly.” Applying State v. DiGuilio, 491 So. 2d 1129 (Fla. 1986), the court held the State had not shown beyond a reasonable doubt that there is no reasonable possibility the testimony contributed to the verdict. It reversed the convictions and sentences in the substantive case and remanded for a new trial.
The court affirmed the remaining rulings without discussion, other than the six-person jury challenge, which it rejected under Guzman v. State, 350 So. 3d 72 (Fla. 4th DCA 2022), and Cunningham v. Florida, 144 S. Ct. 1287 (2024), with a But see citation to Kian v. State, 421 So. 3d 439 (Fla. 4th DCA 2025), noted as “cert. granted.”
In the probation case, the court found Faustin’s request to reverse the revocation — based on his arguments in the substantive case — “not adequately briefed” and affirmed the revocation. Because of the new-trial order, however, it vacated the probation sentence and remanded for resentencing with a corrected scoresheet.
Why It Matters
The opinion draws a line between an investigating officer’s account of what he did and a speed opinion produced by applying a trained-in formula. The latter, the Fourth District held, is expert testimony subject to section 90.702, and here its role corroborating other evidence on a central issue meant it was not harmless. The ruling came where the State essentially conceded error, and the court left open whether momentum analysis can be reliable when properly performed.
The Opinion
Download the full opinion (PDF)
| Court | Fourth District Court of Appeal |
| Case No. | 4D2024-2667 and 4D2024-2669 (consolidated) |
| Lower Court | Circuit Court, Seventeenth Judicial Circuit, Broward County (Judge Michael Lynch) |
| Opinion by | Judge Ciklin (Judges Gross and May concurring) |
| Decided | October 7, 2026 |
| Result | Affirmed in part, reversed in part, and remanded: new trial in the substantive case; probation revocation affirmed, VOP sentence vacated for resentencing with a corrected scoresheet |