Biology/Sociology

One in a Million

DNA fingerprinting (the use of a person s DNA to identify them) has become a hot topic in the field of law enforcement as well as the entire world. The controversy exists on whether or not it should be admitted in court as evidence at this time. Some experts believe that the present technology allows DNA fingerprinting to be used in cases for positive identification (proof that the DNA match was at the scene of the crime) because of the extreme unlikeness that a tampered tissue cell could come up with an exact match. The chances are stated to be somewhere between one in ten million and one in ten billion. Other experts believe that since there is no current standard for labs to test DNA samples and there is a possibility of great human error in a very complicated ordered set (DNA) that a positive identification could be made on someone who is far from the actual perpetrator. Both sides believe that DNA can identify a person, they just disagree on whether or not that is possible at this point in time.

DNA fingerprinting takes a sample DNA (victims, suspects, etc.) and counts the number of variable number of tandem repeats (VNTR) in a person s DNA string. The repeats for four or five common repeating gene groups are counted and compared to a known sample (again the suspect, victim, etc.) for a match up. This may sound like scientists are only counting or four or five numbers when in reality they are counting on four or five sets of many numbers. The chances of similar numbers coming up in life (not the court case) are between one in a million and one in a billion.

The experts in favor of using DNA fingerprinting now use the odds of one in a million having similar enough DNA strands to even come close to misidentifying anyone.

They believe that since the contamination factor can come into play the evidence should only be used to identify for positive proof. The chances that a contaminated sample could come close to matching with a suspect s sample are even worse than the one in a billion odds mentioned before. These experts believe that using four or five sets of numbers clears any doubt of verification once and for all.

The experts who believe it shouldn t be used claim that our present technology disrupts the accuracy of actual DNA fingerprinting. They agree the odds of misidentifying are slim, but they are still too large to accept in a court of law. An example they use is the miscalculation factor in VNTRs. The difference between 109 and 119 is so slim that it could be calculated as the same by today s standards when in truth that may be a different person all together. The factor of human error is easy to see also, especially in the case of Jose Castro when witnesses for both the defense and the prosecution found the evidence analyzing techniques inadequate (it should be noted that the defendant did plead guilty to the crime of murder he was charged with and was found guilty).

DNA fingerprinting is at a very impressive standard at this time for identify people and there is no doubt about whether or not it should be used in the future. At this point I would assume that a one in a million chance is enough to be admissible in a court of law for positive identification. I could not blame a state for not admitting it either.