by Doug Ankney

In a unanimous decision, the Supreme Judicial Court of Maine held that the trial court erred in admitting expert testimony comparing partial, sock-clad bloody footprints found at the crime scene to sample prints taken from the defendant. The Court determined that the State’s expert did not employ the field’s recognized methodology and otherwise did not employ the field’s recognized methodology; failed to demonstrate that his approach satisfied Rule 702’s reliability threshold; and did not articulate his ultimate opinion in terms useful to the jury..

Background

On April 21, 2022, Kimberly Neptune was discovered deceased in her Pleasant Point, Maine, apartment, having suffered 484 stab wounds. The State indicted Kailie Brackett and Donnell Dana, Jr., for murder. Brackett and the victim had been close friends who saw each other frequently, and Brackett knew the victim dealt Xanax and where she stored her supply.

At trial, the State presented evidence that, the day before the murder, a witness overheard Brackett state that the victim had stolen money and “was going to pay for it.” On the day the body was discovered, Brackett withdrew over $700 from the victim’s bank accounts and made purchases using her debit card. Surveillance footage showed an individual leaving the victim’s apartment building the morning of April 21, and a similar jacket was later photographed in Brackett’s home. However, no fingerprints suitable for comparison were recovered from the crime scene. DNA samples from bloodstains identified the victim as the major contributor, with the codefendant Dana and unknown males as minor contributors. Brackett’s DNA was absent from all samples.

Crime scene investigators documented bloodstained footprints – impressions of feet, not footwear – in the victim’s bedroom and on the carpeted stairs. Prior to trial, the State moved to admit testimony from Dr. Michael Nirenberg, a podiatrist, comparing four partial, sock-clad prints from the scene to prints taken from Brackett while incarcerated. Brackett opposed the motion, presenting testimony from Dr. Alicia McCarthy. Following an evidentiary hearing, the trial court permitted both experts to testify.

At trial, Nirenberg concluded that “moderate” evidence supported the proposition that Brackett made the crime scene prints, while “moderately strong” evidence indicated Dana did not. McCarthy challenged the scientific validity of Nirenberg’s approach extensively. The jury deliberated for three days, ultimately convicting Brackett while deadlocking on Dana. Brackett was sentenced to 55 years in prison. She timely appealed.

Analysis

The Court reviewed the trial court’s foundational reliability finding for clear error and its ultimate admissibility decision for abuse of discretion. Under Maine Rule of Evidence 702, a qualified expert “may testify in the form of an opinion or otherwise if such testimony will help the trier of fact to understand the evidence or to determine a fact in issue.” Rule 104(a) requires the court to resolve preliminary questions regarding witness qualification before admitting evidence.

The Court noted that admissibility depends on whether testimony will assist the jury and whether the expert possesses adequate qualifications to provide such assistance. See Searles v. Fleetwood Homes of Pa., Inc., 878 A.2d 509 (Me. 2005). Importantly, before addressing these questions, the trial court must first determine “whether there is sufficient scientific basis” for the proposed testimony. When expert testimony involves newly applied scientific principles, the Court explained, trial courts “may consider whether the scientific matters involved in the proffered testimony have been generally accepted or conform to a generally accepted explanatory theory” when assessing threshold reliability. State v. Bickart, 963 A.2d 183 (Me. 2009).

The Searles Court identified six factors that courts may consider: (1) whether supporting studies involve facts similar to those at issue; (2) whether the hypothesis has undergone peer review; (3) whether the expert’s conclusion has been tailored to the case’s facts; (4) whether other experts attest to the testimony’s reliability; (5) the nature of the expert’s qualifications; and (6) where causation is asserted, whether a scientific basis exists for that relationship. The Court stated unequivocally: “If an expert’s methodology or science is unreliable, then the expert’s opinion has no probative value.”

The Uncertain Status of Forensic Podiatry as a Validated Science

The Court examined the scientific foundation underlying forensic podiatry footprint comparison, drawing extensively on reports from the National Academy of Sciences (“NAS”) and the President’s Council of Advisors on Science and Technology (“PCAST”). The 2009 NAS Report concluded that, excepting DNA analysis, no forensic discipline had been empirically demonstrated to reliably connect evidence to a specific source. Feature-based comparison methods, including footwear impression examinations, were identified as particularly problematic because they involve subjective visual assessments. Notably, forensic podiatry received no mention whatsoever in that report’s analysis of forensic disciplines.

The 2016 PCAST Report identified certain methods, such as fingerprint analysis, as having achieved foundational validity, while others remained problematic. Again, forensic podiatry was absent from discussion. Both experts agreed that black-box studies – empirical tests measuring examiner accuracy and establishing replicable error rates – represent the gold standard for validating forensic methodologies. McCarthy testified, without contradiction from Nirenberg, that no such studies exist for footprint comparison.

The record further revealed that forensic podiatry’s status within the broader forensic-science community remains unsettled. McCarthy testified that neither the Organization of Scientific Area Committees (“OSAC”) nor the International Association for Identification (“IAI”) recognizes forensic podiatry as an accepted discipline, and Nirenberg’s testimony did not establish otherwise. He acknowledged uncertainty regarding OSAC’s acceptance and disputed IAI’s non-acceptance by pointing to his participation on an IAI forensic podiatry subcommittee. The European Network of Forensic Science Institutes similarly does not list forensic podiatry among its working groups or issue related guidelines. The Court observed that while this lack of recognition does not preclude admission, “it does suggest that more probing of the science is necessary.”

Nirenberg’s Methodology Failed to Meet Reliability Requirements

Even assuming forensic podiatry could satisfy general reliability standards, the Court determined that Nirenberg’s specific approach was deficient. The recognized methodology within the field since 2012 is the Reel technique, which employs standardized linear and angular measurements. Nirenberg acknowledged in his own writing that this methodology “is considered the best method to measure a footprint.” But he did not employ it, claiming the partial nature of the crime scene prints prevented its application.

What methodology Nirenberg did employ remained unclear from the record. He identified 60 features by “visualizing” shapes within the prints, then determined that 50 were “similar” to Brackett’s sample prints. These features derived from no standard guide, and the number selected varied case by case. When asked whether objective scoring would permit another examiner to replicate his results, Nirenberg answered no. He conceded that two different examiners could reach different conclusions because the determination was purely subjective.

McCarthy identified numerous problems affecting comparison reliability: the unknown thickness of socks worn at the scene versus those used for prison samples; the fact that bloodstained prints sprayed with Leuco Crystal Violet were photographed two days later rather than immediately, causing distortion; potential weight changes affecting print size over the year between the crime and sample collection; and differences in printing surfaces. Nirenberg acknowledged these concerns were “valid” but dismissed them as falling within a five-millimeter margin of acceptable variation, without analyzing how individual factors might impact measurements and without explaining why this margin would apply uniformly regardless of circumstances.

Nirenberg’s Conclusions
Were Not Useful to the Jury

Beyond reliability concerns, the Court determined that Nirenberg’s conclusions failed to assist the jury meaningfully. See Tolliver v. Dep’t of Transp., 948 A.2d 1223 (Me. 2008). His ultimate opinion was simply that Brackett “could still have made that footprint.” Using a scale he said he derived from the European Network – although, as the Court noted, he did not say that the European Network applied that scale to foot comparisons – he characterized the evidence as “moderate” that the prints were Brackett’s. When pressed to define this term, Nirenberg could only describe it relative to other scale positions, stating each step represented 10 times the strength of the step below. He could not identify what portion of the population would produce prints fitting the “moderate” category, the Court observed.

The Court concluded that this testimony was “so abstract, vague and speculative that its relevance and probative value was virtually nil.” State v. Tellier, 526 A.2d 941 (Me. 1987).

Prosecutorial Mischaracterization Compounded the Error

The Court stated that the prosecutor’s closing and rebuttal arguments transformed Nirenberg’s equivocal testimony into definitive proof. The prosecutor stated that Brackett’s footprints “matched” and declared: “What we know is that her footprints were found at the scene.” This mischaracterization, combined with unreliable expert testimony, required reversal because the Court could not conclude the errors were harmless. See State v. Mangos, 957 A.2d 89 (Me. 2008) (vacating judgment because the erroneously admitted evidence was not harmless because it scientifically linked the defendant to the clothing worn during the crime).

Three factors supported this conclusion, the Court explained. First, excluding the footprint evidence, the case against Brackett was sufficient but not overwhelming; there were no eyewitnesses and no other forensic evidence connecting her to the crime scene. Second, the jury convicted Brackett while deadlocking on Dana, and the primary distinction between them regarding physical evidence was Nirenberg’s “moderate” versus “moderately strong” conclusions, which the prosecutor expressly contrasted. Third, expert evidence “may be assigned talismanic significance in the eyes of lay jurors,” United States v. Frazier, 387 F.3d 1244 (11th Cir. 2004), and when prosecutors compound erroneous admission by bolstering that testimony with their own authority, vacatur is required.

Conclusion

The Court reaffirmed the essential gatekeeping function that trial courts must perform when evaluating expert testimony, stating that scrutiny must be “particularly acute when a field has not yet gained recognition within the forensic science community.” Because the footprint comparison evidence lacked sufficient reliability, was not presented in terms useful to the jury, and was mischaracterized by the prosecution, the conviction could not stand, the Court concluded. However, because the remaining evidence was legally sufficient, double jeopardy does not bar retrial.

Accordingly, the Court vacated the judgment and remanded for further proceedings. See: State v. Brackett, 2026 Me. LEXIS 12 (2026).

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