Matthew T. Mangino: DNA evidence comes full circle
The criminal justice system has embraced the nearly unchallenged power of DNA evidence. The connection of a suspect to a victim or crime scene by DNA evidence is considered the gold standard among criminal investigators.
In a stunning bit of irony, as DNA analysis has improved and the access to potential samples increased exponentially, DNA has opened the door to wrongful arrests and convictions.
The emerging concern, long considered a theoretical risk but only now confirmed by a variety of studies, is that the presence of DNA does not prove that a suspect actually visited the scene or directly touched the object in question. DNA can be transferred by other means.
DNA analysis once required substantial samples of blood or other bodily fluids in order to create a DNA profile. However, technological advances in the study of DNA now make it possible to produce a complete genetic profile of a suspect from just a few cells found on a victim or object.
Attorney Erin E. Murphy, author of “Inside the Cell: The Dark Side of Forensic DNA” said, “When you consider that over 10,000 cells can fit on the head of a pin, it becomes clear that the days of testing only large, visible stains are long past.”
According to Christopher Zoukis in Criminal Legal News, scientists learned as early as 1997 that in addition to primary or direct transfer — DNA transferred from an individual to an object — DNA can also be transferred from the touched object to a second person. This phenomenon, known as secondary DNA transfer, should have thrown up an immediate red flag in the world of forensic DNA analysis — it did not.
Twenty-one years later — with DNA analysis evolving rapidly — there has been an alarming lack of analysis of secondary transfer by forensic scientists. Cynthia Cale of the Human Biology Program at the University of Indiana published a 2016 study in the Journal of Forensic Science in which she and her colleagues confirmed the secondary DNA transfer phenomenon.
The study concluded that secondary transfer of DNA through intermediary contact is far more common than previously thought, a finding that could have serious implications for the criminal justice system.
Cale’s experiment included people exchanging long handshakes immediately prior to handling knives. When each knife was tested, the DNA of the person who handled it was found in almost every case. However, 85 percent of the time the tests found the DNA profile of a person who never touched the knife. Perhaps even more shocking was that 20 percent of the time, the non-touching person came back as the primary and in some cases, the only contributor of DNA.
The problem is simple. The science has outpaced common sense. DNA is not a magic bullet. The mere fact that it exists does not mean a conviction is inevitable. DNA must be analyzed and carefully considered along with all the other evidence in a case.
For instance, if a suspect’s DNA is found at a crime scene and it was later learned that he was in jail when the crime was committed that is pretty good proof that his DNA somehow ended up at the crime scene, even though he never did. On the other hand, if a suspect with a DNA connection tells police he was watching television with his girlfriend when the crime was committed will he be given the same deference?
How far will police go to determine if the DNA was transferred to the crime scene by some person, or some object, other than the suspect him or herself?
DNA has helped exonerate individuals wrongfully convicted, at times after long prison stays. DNA has long been lauded for solving “cold cases,” investigations that have long remained dormant. Most importantly, DNA has helped convicted offenders who may have otherwise evaded prosecution.
It would be unfortunate if advances in DNA technology would be responsible for placing innocent people in jeopardy because trace evidence was used to falsely place those people at a crime scene.
— Matthew T. Mangino is of counsel with Luxenberg, Garbett, Kelly & George P.C. His book The Executioner’s Toll, 2010 was released by McFarland Publishing. You can reach him at www.mattmangino.com and follow him on Twitter @MatthewTMangino.