Juries in Georgia and around the country tend to find the results of deoxyribonucleic acid analysis extremely compelling, but DNA evidence can be used to free people from prison as well as send them there. DNA can be found in the cells of all animals, and it determines how organisms develop and function. When DNA tests are conducted correctly using tissue samples that have been collected and handled properly, the results are extremely accurate.
Most people first learned about the accuracy of DNA testing in the late 1980s and early 1990s when media outlets began running stories about wrongly convicted individuals being released from prison after spending decades behind bars. Their convictions were overturned when the DNA analysis of blood or other biological material proved that another person had committed the crime. In the subsequent decades, law enforcement agencies around the country have built DNA databases that can be used to identify possible suspects.
DNA testing was originally performed using a technique known as restriction fragment length polymorphism, but the polymerase chain reaction method is more commonly used today as accurate results can be produced using far smaller tissue samples. The science is so accurate because only identical twins have the same DNA. According to most experts, the chances of an individual being misidentified by a properly conducted DNA test are about one in a billion.
While the results of DNA analysis may be extremely accurate, techniques such as RLFP and PCR are not infallible. When faced with seemingly incontrovertible DNA evidence, experienced criminal defense attorneys may call attention to the actions of the police officers and forensic scientists involved rather than question the scientific merits of the techniques used. DNA test results may be unreliable or misleading if sloppy collection and handling protocols led to tissue sample contamination, and judges may exclude this evidence entirely during a criminal trial if crime labs deviated from strict testing procedures.