Pennsylvania prosecutors use TrueAllele in homicide guilty plea

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DNA transfer for lawyers

M.W. Perlin, "DNA transfer for lawyers", Allegheny County Courthouse - Continuing Legal Education, Pittsburgh, PA, 22-Feb-2019.


PowerPoint presentation of Dr. Perlin's talk.

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DNA has tremendous power in the courtroom. Typically introduced by a prosecutor for establishing probative connections between crime scene and defendant, the defender's task is to neutralize that probative power. DNA's message is that someone has left their biological material in an unexpected place, where it doesn't belong; the rejoinder is that the DNA evidence is entirely expected to be there.

How is this done? An increasingly common approach is through the defense argument of "DNA transfer." Here are some examples.

  1. Why is the defendant's DNA on the victim' s underwear? Because it transferred there in the laundry. He's innocent.
  2. How did the defendant's DNA get on the weapon? Because it was wrapped in a towel taken from his home. He's innocent.
  3. When was the defendant's DNA left in the deceased's pants pocket? The prosecutor says it was when he rifled through clothing to steal the victim's wallet. The defense replies the two men knew each other - it's only innocent DNA transfer that happened at an earlier time, before the crime occurred.

DNA transfer gives defenders hope - and prosecutors anguish. How does one respond to a vague assertion that can introduce reasonable doubt about solid DNA evidence? The rebuttal comes from established science that can show why the proffered DNA transfer is not likely, given the facts of the case and DNA science.

This CLE course will teach lawyers about DNA evidence, transfer alternatives, and arguments that can be made by both sides. Drawing from actual criminal case fact patterns, students will learn how to effectively attack and defend DNA evidence using recent methods and strategies from DNA science and law.

The CLE will be taught by Dr. Mark Perlin. The course will be held on February 22, from 12:30 to 2:30 pm ET in the Gold Room on the fourth floor of the Allegheny County Courthouse. Hosted by the Allegheny County Office of the District Attorney and sponsored by the Justice Through Science Association, this CLE will provide two hours of substantive CLE credit. A $15 fee is required and attendees can pre-register with Lynn Gettings (phone: 412.350.3110, email:

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Mark Perlin, PhD, MD, PhD is President of Justice Through Science. He is also Chief Scientist and Executive at Cybergenetics, a Pittsburgh-based company. An expert in computational genetics for over 25 years, he developed the TrueAllele computer system for interpreting complex DNA evidence. Dr. Perlin has worked on over 500 criminal cases, testifying about objective computer DNA evidence in over 50 trials in state, federal, military and foreign courts. He has testified as a DNA expert in over a dozen Frye or Daubert admissibility hearings, and lectures frequently at continuing legal education programs. He holds doctoral degrees in Mathematics (City University of New York) and Computer Science (Carnegie Mellon University, Pittsburgh, PA), and a medical degree (University of Chicago). He was a Senior Research Scientist in Computer Science at Carnegie Mellon University, and adjunct faculty in Human Genetics at the University of Pittsburgh. He is currently adjunct faculty in the Bayer School of Science at Duquesne University.

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