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Monday, June 2, 2014

Criminal Justice Quote: DNA Analysis

     DNA "fingerprinting" has nothing to do with actual fingerprints; the term simply means profiling or identifying….Though it became a byword among the public during the O. J. Simpson trial in 1995, it was first developed a decade earlier, in England.

     The basic principle of DNA testing is that every human being who is now alive, or who has ever lived throughout all time, owns a unique set of genes. Every cell of every human being contains a code unique to that individual, like the bar codes on supermarket products.

     This DNA--deoxyribonucleic acid--is the principal carrier of genetic data in human beings and in almost all other living organisms (with the exception of certain viruses). When studied through an electron microscope, its shape is that of a spiraling rope ladder, scientifically known as a double helix.

     Because each person's DNA is unique, when samples are taken from blood, semen, or other bodily fluids at a crime scene or during an autopsy, and are then compared with the DNA of either the victim or the victim's suspected killer, a match is either made, or not. If it is made, then the degree of certainty that this DNA belongs to this person is authoritative. By that I mean that the standard for most DNA testing is that there be no more than one in a million chances that the test is in error. In practical terms, this means there is little or no chance for error at all. This one-in-a-million standard, moreover, is conservative.

     In DNA tests, possible error is ranked at one in 5 million, or sometimes one in 10 million….

Frederick Zugibe, M.D., Ph.D. and David L. Carroll, Dissecting Death, 2000

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