If you have been charged with a serious criminal offense there is a good chance that law enforcement investigators will attempt to use DNA to prove the accusations against you. Like most people, you likely have some idea how DNA evidence works given the fact that there are a seemingly endless number of police crime dramas on television that all refer to the use of DNA evidence at one time or another in one of their “cases.” If your freedom and future are on the line, however, it is not a good idea to rely on the way evidence is portrayed by Hollywood screenwriters. In an effort to help educate defendants about the manner in which DNA evidence is used in a criminal case, a Cass County criminal defense attorney has offered to explain the basics of DNA and its use as evidence in a criminal prosecution.
What Is DNA?
A DNA molecule is a long, twisting chain known as a double helix. DNA is made up of four nucleotides:
These nucleotides exist as base pairs that link together like the rungs in a ladder. In human cells, DNA is tightly wrapped into 23 pairs of chromosomes. One member of each chromosomal pair comes from your mother, and the other comes from your father. In other words, your DNA is a combination of your mother’s and your father’s DNA. Although 99.9 percent of the DNA from two people will be identical, the 0.1 percent of DNA code sequences that vary from person to person are what make us unique. Therefore, unless you have an identical twin, your DNA is unique to you and no one else’s will match yours when tested.
Where Do the Police Get the DNA They Test?
The best thing about DNA evidence, from the perspective of law enforcement authorities and prosecutors, is that DNA evidence can be found in so many different places. Moreover, all the cells in your body contain the same DNA. Therefore, your DNA can be extracted from your hair, your blood, your saliva, and even tiny pieces of skin found underneath a fingernail. A perpetrator will frequently leave DNA evidence behind in one of these forms, making it easy for the police to run a DNA comparison.
How is DNA Tested and Compared?
Once a possible DNA sample has been collected from a potential suspect, the DNA is isolated from the cells and millions of copies are made, using a method called ‘polymerase chain reaction’, or PCR. PCR uses a naturally occurring enzyme to copy a specific stretch of DNA over and over again which makes the genetic code easier to analyze. The DNA molecules are then split at particular locations to separate them into known ‘chunks’ and the code at those specific points is analyzed to create a DNA “fingerprint.” The results of the test on the suspect’s DNA can then be entered into a national data base to see if it matches anyone already in the data base or it can be compared to the DNA of a specific person to check for a match.
Is DNA Testing Accurate?
When he samples are handled correctly and the tests are run properly, DNA testing is highly accurate; however, it is not 100 percent accurate. When the two samples tested do not have any markers in common it is safe to conclude that the samples are not from the same person. When two samples do have markers that match, it is almost certain they are from the same individual but there remains a very small possibility that they are not a match. The more markers tested the more likely it is that the two samples are a match. When six to ten markers are tested and all match the odds that they are not from the same person is about one in one billion.
If you have been charged with criminal offense in the State of Nebraska it is certainly in your best interest to consult with an experienced Nebraska criminal defense lawyer right away. In Nebraska contact Petersen Criminal Defense Law 24 hours a day at 402-509-8070 to discuss your case with an experienced criminal defense attorney.