At the same time, the DNA is treated with chemicals or heat to cause the fragments to unzip into two single strands. Interpreting the DNA print. Most exclusions are obvious. If not so obvious, the bands are measured through the computer. Determining a match.
Labs conduct population studies based on samples from blood banks.
That provides a database for determining the odds of a match within the general population. Some argue that there are variations within racial and ethnic groups that skew the odds of a coincidental match - a position Simpson's defense is adopting. The prosecution argues that statistical analyses are founded on basic mathematical principles. For the more conclusive RFLP test, odds of a chance match ranges from one in more than 10,000 to one in hundreds of thousands or even millions. For PCR analysis, the range is about one in 100 to one in 2,000 - leaving it wide open for the defense to argue that the probability of a coincidental match is high in a city of 3 million.