DNA And Criminal Investigations
Many people assume that DNA use in criminal forensic investigations is an American technology. In fact, the first murder convicted through the use of DNA was in England in 1983. Colin Pitchfork was successfully tried and convicted of the murder and rape of two children in Leicestershire, England.
The scientist behind this early testing, which included testing the blood and saliva testing of over 500o men in the area, was Alec Jeffreys. A genetic professor, he worked with others at the Forensic Science service to develop the extraction techniques and to complete the initial testing that eventually helped to get the conviction.
The Evolution of DNA Testing and Results
While DNA testing is very accurate, it is not the sole piece of evidence that can be used for a conviction through the courts. Today, DNA testing is much more rapid but, with the number of testing requests, it can take months to complete.
In the original tests, blood or saliva had to be present for both the sample as well as all comparisons to the sample. Now, with greater sensitivity, it is possible to test for touch DNA. This tests skin cells left on a surface, which is an amazing advance for the science in just three decades.
In addition to testing for one DNA profile, tests can now distinguish multiple sources of DNA in a sample and identify those individual profiles. In the next few years, it is very likely that police forces will have access to DNA equipment that can run samples in a few hours without the need of complicated sample processing.
How it Works
In the early days of DNA testing in criminal cases, scientists used gel electrophoresis to separate the DNA fragments. This process could take up to eight weeks to complete.
In the early 90s, the tests used STRs, which are shorter sequences of repeating units. The result is a shorter fragment to determine the unique characteristics. Gel electrophoresis was also replaced with capillary electrophoreses, which allows rapid determination of the peaks in the sample to create the unique pattern on an electropherogram. These peaks create the markers which can be compared to databases to determine a match.
The Creation of CODIS and Beyond
CODIS or Combined DNA Index System, is a database that stores DNA profile entries from police departments. To meet CODIS standards, all new profiles entered into the system must contain 20 loci for comparison.
In addition, new software can fill in missing sequences and eliminate the problem with inconclusive tests in the past. The software generates match statistics, which are required in court to provide a probability for matches with all DNA testing.
The science of DNA testing in criminal cases is rapidly evolving. With faster testing and without the need for complex lab procedures for collection, rapid DNA testing is just around the corner.
To learn more about the scientific use of DNA in criminal cases, check out our blogs or read our reviews at Genomelink. We will keep you posted as new and exciting advances occur in this fascinating area of science.