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What is a DNA transfer and why is it a problem?


Genetic evidence, in the form of DNA, is increasingly being used in modern courtrooms, and advances in genetic material testing processes have even blown open a number of cold cases in recent years. It’s only natural for juries and judges to think that DNA is the “end-all, be-all” of evidence – something that’s utterly irrefutable.

But, is it? DNA evidence can be useful, but the advances in testing could make it more likely that someone could be convicted by mistake.

It takes only tiny amounts of DNA to produce results

A decade or so ago, lab technicians needed a pretty good sample of genetic material to run their tests and identify the person who contributed it to a crime scene. Today, a few skin cells or a single hair could be plenty to make a match.

And that’s the problem. Trace amounts of genetic material can easily be transferred from one person to another over great distances – and that genetic material can end up in surprising places.

Consider the example of a homeless California man who nearly went to death row after his DNA was found on the fingernails of a wealthy home invasion victim. The accused, who suffered from alcoholic blackouts, even questioned his own guilt. However, it turned out that he couldn’t have committed the crime because he’d been unconscious and under watch at a local hospital at the time of the murder.

How did his DNA get to a dead man’s fingernails? The same paramedics who took the accused to a hospital earlier that night eventually responded to the murder 10 miles away, carrying the man’s genetic material with them on their shoes, clothes and equipment.

Contaminated crime scenes are likely more common than people realize, and DNA evidence is not irrefutable. When you’re charged with a violent crime and DNA is a factor, don’t assume that your case is hopeless.

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