DNA, also called deoxyribonucleic acid by scientists, is often used as important evidence by prosecutors in criminal law trials. DNA is a set of molecules found in the human body. Similar to a fingerprint, each person in the world has a different and unique DNA profile. Because each person’s DNA profile is different, DNA matches can be used by criminal prosecutors to help prove to a jury that the suspect facing criminal charges is most likely the person who is guilty of committing the crime.
DNA can unknowingly be left behind by a suspect at a crime scene and later discovered, tested, and analyzed by careful investigators. DNA is found in blood, hair, saliva, teeth, fingernails, skin cells, and bodily fluids including semen. Crime scenes where DNA is commonly found are typically places where violent crimes occurred, including rape, murder, kidnapping, and other incidents involving physical confrontations.
If a suspect’s DNA is found at a crime scene, scientists and law enforcement officials can gain access to a national DNA database that is filled with DNA samples taken from criminal offenders. The DNA database, called the Combined DNA Index System, is used to compare a suspect’s DNA to the DNA of hundreds of thousands of convicted criminals.
This process is sometimes called DNA profiling. If a DNA match is found by law enforcement officials, the prosecution will use this information as evidence to try to prove that the suspect on trial is the person who committed the criminal act.
Finding DNA at a crime scene does not always lead law enforcement agents to find the person who is guilty of committing a crime. In some cases, a person’s DNA may be found at a crime scene, but that person was not involved in committing the crime.
Sometimes, a DNA sample may be incomplete, damaged by age or weather, or mishandled by investigators. In these cases, the DNA sample is considered to be inconclusive evidence and might not be used by criminal prosecutors.