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SINCE 1986, defendants have been losing criminal trials on the basis of one piece of evidence: DNA. Referred to by many as the “CSI Effect,” DNA has long been the gold standard as it pertains to evidence admitted in criminal courtrooms. What has flown under the radar, however, is the rising popularity of probabilistic genotyping—a method of analyzing DNA mixtures containing miniscule fractions of more than one person’s DNA.

Although seemingly beneficial, glaring errors can arise in the use of this upand- coming technology that can directly impact the outcome of a criminal case. Variability in results, the inaccessibility of the computer codes controlling the programs, and the inherent biases inputted into the source code are just the beginning. Additionally, probabilistic genotyping has no way of differentiating between DNA from an individual who actually touched the surface from which the DNA sample was taken, and DNA that is transferred through “touch-transfer DNA.” What’s the latter concept, you ask? A 1997 scientific finding that proved people leave behind DNA on objects held for periods of time as short as 15 minutes. Even more shocking than that, this same study unveiled that when people come into contact with one another, they risk transferring their DNA and any other DNA they might have on their person to the individual with whom they have contact. In other words, anyone who unknowingly comes into contact with someone who later commits a crime risks having their DNA left behind at the crime scene despite never being there.

This unique evidentiary issue has arisen nationwide, and it’s no stranger to Maryland courts. In fact, the Office of the State’s Attorney for Baltimore City started relying upon probabilistic genotyping approximately 10 years ago in its criminal prosecutions. Since then, they have secured hundreds if not thousands of convictions through reliance on this technology. The legal landscape under which this evidence was admitted since its inception, however, changed drastically when the Court of Appeals of Maryland decided Rochkind v. Stevenson, 471 Md. 1 (2020). In its opinion, the Court adopted the broadly accepted Daubert standard for determining the admissibility of expert testimony at trial in lieu of Maryland’s long-standing Frye-Reed standard. With this change, the Court opened the door for criminal defense attorneys to challenge the admissibility of probabilistic genotyping through the testimony of forensic scientists at trial.

Because of the significant upheaval of Maryland’s legal landscape in light of the Rochkind decision, now is the time for criminal defense attorneys to stop accepting the broad admission of probabilistic genotyping evidence against their clients. TrueAllele, one of the primary technology providers in the probabilistic genotyping space, as well as the provider relied upon by the Office of the State’s Attorney for Baltimore City, should not be blindly trusted to produce accurate results. The company has failed to address the concerns raised by the President’s Counsel of Advisors on Science and Technology (PCAST), an objective committee created by the Obama Administration to look into the status of forensic sciences in the United States. Specifically, TrueAllele has failed to run the validation studies recommended by PCAST and has instead claimed it can accurately read DNA samples containing up to 10 contributors. Stated simply, criminal defendants are being subject to the use of evidence that isn’t objectively reliable, unbiased, readily available for review, or entirely accurate. As has become clear since the beginning of the courts’ reliance on forensic science, not every method can be trusted in an arena where the stakes are as high as one losing their freedom.

1 Daniel P. Mooney, Esq., is an associate at The Cole Law Firm LLC in Baltimore.