Deoxyribonucleic acid (DNA) is a hereditary material that serves as a map of a person’s genetic make-up. The same pertinent information is included in all of the cells of the human body. Because of the unique properties of DNA, law enforcement can now positively identify criminals and prove the innocence of people who are unjustly accused of crimes.

Collecting DNA Samples

The DNA evidence has to be carefully preserved to ensure accuracy of the findings. The collection of DNA is a meticulous process, and certain rules must be followed to not contaminate the samples. The samples that are easiest to collect are bodily fluids such as blood, saliva, mucus and semen. Hair, teeth and fingernails are typically examined postmortem and used in autopsies. DNA testing is performed in any criminal case where traditional methods of proving the crime are not sufficient to obtain certain analysis. On many occasions, when the body is missing, the physical evidence, such as clothes, cigarettes and weapons, are examined for the presence of DNA to find the connection between the crime and the perpetrator.

Special precautions are taken during the collection of evidence. All law enforcement personnel involved at the crime scene are required to wear gloves. When they collect the samples, they must store them independently of each other to avoid mistakes and integration of samples. The DNA samples are stored in paper containers and protected from sunlight and air exposure. Plastic bags are avoided, as they collect moisture and compromise the properties of the collected samples.

How a Forensics Team Uses DNA

Once the samples are gathered, a genetic fingerprinting technique (also referred to as DNA profiling) is used to identify people involved in the crime. A team of biologists, lab technicians and medical experts reviews the evidence and matches or dismisses the connection of the existing samples to the crime scene. The findings are routinely forwarded to the Combined DNA Index System (CODIS), where the data is stored for any future reference. CODIS preserves the information and has proven to be invaluable in the identification of suspects from around the globe. Currently, all states require that DNA samples are collected from the offenders and deposited in the database of CODIS.

All examinations, documentation and photographs taken at the crime scene are combined with the DNA findings and forwarded to the appropriate authorities in efforts to solve the crime. All evidence pooled together helps to reconstruct the occurrence and arrive at the proper conclusions, assuring that the correct individual is proved of the crime committed or released.