Brief filed: 12/08/2025
Documents
United States v. Tyler Scott Johnston
2nd Circuit Court of Appeals; Case No. 25-753
Argument(s)
After extensive briefing and a two-day evidentiary hearing, the District Court issued a detailed opinion excluding the DNA evidence as unreliable under Daubert because of the gaps in the capability of the specific lab and the government’s failure to provide the lab necessary facts, combined with the unusually complex testing required because six biological relatives used a certain comforter. United States v. Johnston, No. 23-cr-13 (NRM), 2025 U.S. Dist. LEXIS 59429, 2025 WL 964073 (E.D.N.Y. Mar. 30, 2025). The court also independently excluded the evidence as irrelevant under Rule 401, as no party disputed that DNA from Mr. Johnston, Monica, and Doe was on their own comforter. It further excluded the evidence under Rule 403 because allowing the government to present meaningless DNA testimony as if it was relevant to their case would be unduly prejudicial. The government appealed. Mr. Johnston is represented by Assistant Federal Defender Allegra Glashausser.
Amici argue there is a substantial risk that DNA evidence – particularly complex mixtures evaluated through likelihood ratios (“LRs”) addressing only the “who” question – will be misinterpreted or overstated if presented without the necessary case-related scientific context. The DNA results here are a perfect storm of complex results wrenched out of context, and a prime example of the importance of adhering to methodological limits in forensic science. By setting propositions that do not reasonably reflect the limited universe of potential contributors who may have had contact with the comforter, the analyst generated a flawed LR value, from which the government will ask the jury to speculate that the presence of Tyler Johnston’s and Doe’s DNA can only be due to assault. However, the government is wrong on the science so the District Court’s decision to exclude the DNA evidence was correct.
Author(s)
Lawrence T. Hausman, J. David Pollock, David Loftis, Jenny S. Cheung and Jessica Goldthwaite, Legal Aid Society, DNA Unit, New York, NY; Richard D. Willstatter, Vice Chair, NACDL Amicus Committee, White Plains, NY; Stephen N. Preziosi, Chair NYSACDL Amicus Committee, New York, NY
