TrueAllele solves uninterpretable DNA in mother and daughter double homicide

Back to Newsroom


Reply to nonresponsive Thompson response

Cybergenetics sent a short Reply letter to a Response from emeritus psychology professor and lawyer William Thompson. His Social Science Research Network (SSRN) Response said he would not respond to a Cybergenetics’ SSRN Preprint. Our Preprint had rigorously assessed the scientific merit of a Case Report he had published in the Journal of Forensic Sciences (JFS). This update describes our Reply and provides background.

In a federal drug case, a California defendant had a private laboratory analyze DNA evidence. The lab used STRmix™ probabilistic genotyping (PG) software. Their analysis applied a 40-rfu peak height threshold to a mixture of two people. Just 24 data peaks were input for 14 loci (1.7 peaks per locus). But a two-person mixture can have up to 4 allelic peaks per locus.

With insufficient data for a meaningful mixture analysis, the lab’s STRmix exclusionary likelihood ratio (LR) was only 1/25. The defendant then asked Cybergenetics to examine the same DNA mixture data. TrueAllele® PG analysis used 210 data peaks across all 21 loci (10 peaks per locus) to find a stronger exclusionary LR of 1/1,000,000.

The federal prosecutor held a Daubert hearing to challenge the defendant’s STRmix evidence. The prosecutor didn’t challenge TrueAllele reliability. With the case still pending, the UC Irvine professor published a Case Report in JFS [1]. He gave intricate nonexpert explanations for the differing LR magnitudes. In the face of a simple accurate answer – insufficient STRmix input data – his JFS publication appeared to lack scientific merit.

Cybergenetics responded in SSRN [2] to the JFS Case Report. Our Preprint’s extensive 71-page article exposed 20 conceptual flaws. An LR sensitivity study showed that at lower thresholds STRmix had sufficient data to agree with TrueAllele. A 32-page chart supplement rebutted 120 assertions in the article. Our Preprint used words like mistaken (70 times), irrelevant (14), incorrect (12), ignored (10), biased (8), and misleading (6) to describe the JFS Case Report.

The UCI professor responded in SSRN (2095 words) [3] to Cybergenetics SSRN Preprint. He requested more civil discourse and did not respond to the scientific issues raised. Instead, his Response was directed at the authors. He argued using words like falsehood (8), false (7), fabrication (5), lie (5), and defamatory (2) to describe Cybergenetics’ “hit piece” (3). He gave three “examples of some of their more egregious falsehoods and lies.”

Upon seeing the JFS author’s SSRN Response, the next day Cybergenetics emailed him a reply (344 words) [4]. Our Reply primarily addressed the author’s three alleged “falsehoods”. We only show his summary headings; he argued at greater length in his SSRN Response. (His Response headings in bold, our Reply in italics.)

#1: The prosecutor in the case that I discussed in my article decided not to present a scientific report that I had prepared for him because it was highly partisan and scientifically flawed – JFS author Response heading

You published a Case Report in JFS [1]. It is called a “Case Report” on the front page. No prosecutor ever used your JFS Case Report. There is no dispute here. – Cybergenetics Reply

Note: The JFS author’s Response combines unrelated Preprint phrases to imply things we never said. For example, our Preprint said his JFS Case Report was flawed, and said it wasn’t used. We didn’t say no one used it because it was flawed; that is the author’s own interpretation.

#2: I disclosed the defendant’s name (and other statements)

A. In your Case Report, you showed the defendant’s DNA profile (Table 1). You released his name in the reports you made available on request (Acknowledgments). We stated all this in our Preprint (p. 76, second row).

B. Your JFS Case Report was published while the case was still pending. There was no trial. The plea agreement dropped the DNA-related charge, thanks to TrueAllele.

C. I obtained permission from the defendant’s attorney for mentioning the defendant’s name and the case name in our Preprint.

#3: I published a “ridiculous fabrication” about Perlin’s statements at a PCAST meeting

Recollections may vary. I described what occurred at the PCAST meeting (Preprint, pp. 40-41). Unfortunately, PCAST didn’t transcribe the meeting as I had requested.

Note: Our brief Reply could have added that of the 34 validation studies we gave to PCAST at their 2016 meeting, 14 studies specifically addressed false inclusion rates (false incrimination). Based on documents available at the time of the PCAST meeting, their 2017 assertion about our not wanting to measure false inclusion is indeed ridiculous.

Our Reply letter to the JFS author continued, “If you disagree with our comprehensive analysis of your JFS Case Report, you should explain why. That’s what scientists do. We raised 140 points. You have responded to none of them.”

The Reply concluded, “A refusal to respond concedes that your Case Report has no scientific merit. In which case you should retract your published Case Report from JFS.”


[1] Case Report: Thompson WC. “Uncertainty in probabilistic genotyping of low template DNA: A case study comparing STRMix™ [sic] and TrueAllele™ [sic].” Journal of Forensic Sciences. 2023;68(3):1049-63.

[2] Preprint: Perlin MW, Allan WP, Bracamontes JM, Danser KR, Legler MM. “Reporting exclusionary results on complex DNA evidence, a case report response to 'Uncertainty in probabilistic genotyping of low template DNA: A case study comparing STRmix™ and TrueAllele®' software.” SSRN. 5 June 2023.

[3] Response:Thompson, WC, “Response to False Statements Posted on SSRN by Mark Perlin, CEO of Cybergenetics, and His Employees,” SSRN, 5 July 2023.

[4] Reply: Perlin, MW, “Letter to William Thompson,” 3 August 2023.

Back to top