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Sunday, May 18, 2014

Criminal Justice Quote: The Power of DNA

     Scientists first identified DNA in 1944. Much more recently, early in the twenty-first century, scientists successfully mapped the entire human genome, the sequence of genes on each DNA strand. DNA is found in skin cells, hair, blood, semen, saliva, even teeth and bone, and analysis of it is carried out by using a computer to compare and attempt to match two samples.

     We shed old skin cells and hair constantly, which is why DNA is so often found at the scene of a crime, and DNA samples can be obtained by swabbing inside the cheek or from an unwitting suspect's cigarette butt, coffee cup, or toothbrush.

     Only identical twins and clones have identical DNA. For anyone not a twin, finding a match between one's DNA and a specimen found at a crime site is as close as one can get to proof that the person was involved in the crime. [More accurately, it's concrete proof the DNA donor was there.] It's still circumstantial evidence, but juries tend to find it sufficient to convict a defendant. In the last few years, hundreds of convicted but innocent felons have been pardoned on the strength of DNA analysis.

Robert Mann, Ph.D. and Miryam Ehrlich Williamson, Forensic Detective, 2004 

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