Deoxyribonucleic acid, or DNA, is the nucleic acid which is found in almost all living things that contains the genetic instructions that bring us to life. Much like human fingerprints, human DNA is unique. As a result, DNA forensics has been developed as an accurate and important aspect of many criminal and civil investigations. DNA forensics can be used to analyze blood, hair, semen, saliva, or skin which is left behind at the scene of a crime. Aside from criminal uses, DNA forensics are also used to determine the paternity of a child.
The molecules of DNA form the foundation for our heredity, and DNA is built in a double helix framework that is bonded by hydrogen, which holds together both the purine base and the pyrimidine base. Localized in the nuclei of cells, DNA's two bases extended into the helix from an alternating strain of deoxyribose and phosphate. In essence, DNA can be thought of as a recipe for life. With a recipe, if one ingredient is changed, even slightly, the end result tastes different. With DNA, the slightest variation is what makes us unique human beings.
That same variation is what allows DNA forensics to be a useful tool. In criminal investigations, DNA profiling may be used to test evidence left behind by the perpetrator of a crime. Developed in the 1980s, DNA profiling requires the lengths of a section of DNA found at the scene of a crime to be compared to sections of DNA from a potential suspect to see if they match.
Crime scene DNA can be found in blood, saliva, or semen, as well as hair or skin. The science behind DNA forensics has developed to the point where only the smallest, almost imperceptible trace of blood or other DNA carrier, can provide enough of a sample to conduct DNA profiling. In addition, although human DNA is 99.9% alike, the remaining one percent is different enough to make us unique.
DNA profiling is considered accurate enough for courts, in most jurisdictions, to allow its introduction as evidence. Rape and murder investigations are the most common uses of DNA forensics; however, any time a suspect is sought and there is DNA evidence left behind, it may be used. In many jurisdictions, a court may order a possible suspect to allow his or her DNA to be drawn for a comparison by the issuance of a warrant.
Although criminal investigations are where most people think of the use of DNA forensics, civil paternity cases also use DNA forensics to determine the paternity of a child. Forensics is simply the application of science for use in the legal system. A DNA paternity test can determine who the father of a child is with over a 99.99% accuracy.