Drawback Of DNA

Physical evidence is sometimes called the silent witness, and examination of physical evidence is the way crimes are most often solved (Silverstein, 1996, book flap). As we all know DNA is becoming more and more depended on in the courtroom, as far as determining the guilty and the innocent. However, using DNA testing to determine the culpability of criminals .
             is not viable evidence in the courtroom, because of the possibility of human error, of the deliberate manipulation of test results or of just random chance.
             An example of a DNA evidence error took place in America when various press reports released in early February made mention of a case wherein a local police department confessed to having identified an innocent person as a criminal by a DNA test that was said to be in error. A U.S police agency that had secured near 100 convictions on the basis of DNA testing, admitted that, as far back as April of 1999, they had matched a sample taken from the scene of a burglary to six loci on the DNA molecule of one of 700,000 persons whose DNA was collected in the national database. The suspect was a man with advanced Parkinson's disease, who could not drive and could barely dress himself. He lived 200 miles from the site of the burglary. His blood sample had been taken when he was arrested, and then released, after hitting his daughter in a family dispute. He was arrested despite his protestations of innocence and alibi evidence that he was babysitting a sick daughter at home. Police dismissed these protestations stating that "it had to be him" since the DNA matched. The odds of the arrestee's DNA being wrongly matched against that of the crime scene were said to be one in 37 million (Moenssans 2000). .
             So was the result reported after an examination of six loci an "erroneous" or "false" identification? No. There was indeed a "match" at six loci. What confuses .
             lawyers, judges, laypersons, and indeed the police, who make use of DNA evidence test results, is that they do not understand the true meaning of the statistics used by the experts.