Forensic® News publishes DNA Matters™ – a Special Feature column written by Cybergenetics founder and chief scientist Dr. Mark Perlin.
The Forensic® DNA Matters column explores DNA identification technology – and how it affects people and society – in the context of criminal cases.
- Why forensic genotypes are probabilistic
- How to use the likelihood ratio
- How complex DNA evidence exonerates the innocent
- What forensics owes to Alan Turing
- How to solve a DNA mystery: Part 1
- How to solve a DNA mystery: Part 2
Why forensic genotypes are probabilistic
Friday, April 30, 2021
"Probabilistic genotyping" is now in crime laboratories, courts and the news. But why is this technology "probabilistic"? Where does randomness come into the DNA typing process? And how does "probgen" computing take care of it?
The first DNA Matters column tells the story of a serial rapist in Upstate New York, and the DNA he left on a pair of purple gloves. How crime laboratory processing introduced inherent randomness into the DNA data. And how TrueAllele® probabilistic genotyping resolved the DNA mixture to identify the criminal in the context of his crime.
How to use the likelihood ratio
Friday, May 28, 2021
Forensic scientists report a “likelihood ratio” (LR) for the strength of match between DNA evidence and a suspect. Without a match statistic, DNA can’t be used as courtroom evidence. The entire purpose of forensic DNA science is producing a reliable LR match statistic. But what is a “likelihood ratio”? How is the LR used? When is the LR easy to understand?
The second DNA Matters column tells the story of a cold-blooded killer in Southwestern Pennsylvania, with DNA mixtures found on a gun and a hat. How initial crime laboratory reports gave little information. And how TrueAllele® data analysis revealed likelihood ratios that showed who did, didn’t, and couldn’t have committed the crime.
How complex DNA evidence exonerates the innocent
Friday, June 25, 2021
The third DNA Matters column tells the story of the exonerations of Darryl Pinkins and Roosevelt Glenn.
On a frigid December night in 1989, Darryl Pinkins and Roosevelt Glenn stood on the shoulder of an Indiana highway. Coworker William Durden had been driving them home, until his car broke down. The stranded men set off for help.
Unbeknownst to them, five gang members were cruising along the same Lake County road. They broke into Durden’s car and stole a bag of work coveralls. Later that night, the criminals deliberately bumped into a moving vehicle. After the car stopped, all five gangsters raped the driver. They covered her with a stolen coverall, and drove away.
What forensics owes to Alan Turing
Wednesday, June 29, 2022
The fourth DNA Matters column tells the story of Alan Turing and his contributions to the field of forensics.
British mathematician Alan Turing was born in June 1912. Esteemed as the father of computer science, his Turing Machine revealed the full power of modern computation, while his Turing Proof showed its limits.
At Cambridge University, Turing invented the concepts underlying modern computer software and hardware. In 1939, he joined the Bletchley Park code-breaking unit. Once there, he designed and built the automated computing machinery and algorithms needed to crack Enigma—the Nazi's coding device for sending secret wartime messages.
How to solve a DNA mystery: Part 1
Monday, May 19, 2025
The fifth DNA Matters column presents Part 1 of a two part mystery involving the death of toddler.
It was in May 2020, on a Sunday COVID afternoon. I was in Pittsburgh, with testimony looming that week in the capital case of California v. Manuel Lopez. Zooming from home with Santa Clara Deputy Public Defender (DPD) Kelley Kulick, trying to solve a crazy DNA mystery.
So much evidence making so little sense. Weeks of transcripts from so many witnesses. Nagged by DNA discrepancies – conflicting rectal swabs, immaculate mother, battered child. Something was missing, and we needed an answer real soon.
How to solve a DNA mystery: Part 2
Wednesday, May 21, 2025
The sixth DNA Matters column presents Part 2 of a two part mystery involving the death of toddler.
It was in late May 2020, the Sunday before I would testify in California v. Manuel Lopez. On Zoom, Santa Clara DPD Kelley Kulick and I were still hunting for DNA answers.
Reviewing conflicting pathologist testimony that found the defendant's DNA in the dead toddler's rectum, but afterwards didn't. Studying TrueAllele computer reanalysis that tripled the crime lab's DNA matches, and wove a rich tapestry telling whose DNA was on which evidence items. Asking why Manuel's DNA was on 29 items, but the victim's mother Samantha Torres was on nothing.
Founded in 1994, Pittsburgh-based Cybergenetics innovates advanced computing to get more information out of biological data. Twenty years ago, founder Dr. Mark Perlin invented TrueAllele® probabilistic genotyping for automated human identification from DNA mixtures. The company helped identify victim remains in the World Trade Center disaster, and has helped exonerate ten innocent men.
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