DNA Evidence

DNA evidence refers to any substance that contains human DNA and can tie someone to a crime. In recent decades, as DNA testing has become more accessible and accurate, DNA evidence has come to play a major role in convicting, acquitting and exonerating individuals accused of a crime.

What is DNA?

DNA, which stands for deoxyribonucleic acid, is a double helix, organic material contained within each cell of a person's body. Like fingerprints, every individual has a unique DNA composition, making DNA evidence a definitive link between a specific individual and a crime.

Types of DNA Evidence

Since DNA is in every cell within a person's body, DNA evidence can come from any part of a person that is left behind at the scene of a crime. Common types of DNA evidence include:

• Blood
• Saliva
• Skin cells
• Semen or vaginal secretions
• Hair (including eyelashes, body hair, pubic hair, etc.)

When a piece of DNA evidence is collected from a crime scene for testing, the process is called genetic fingerprinting or DNA profiling.

Testing DNA Evidence: DNA Profiling

After collecting DNA evidence from a crime scene, police will typically analyze the new DNA sample across a database of DNA from known offenders (convicted murders, rapists and others have their DNA kept on file so that cops can quickly identify them, should they repeat their crimes).

If, however, no matches are found, investigators will then likely obtain subpoenas to collect DNA samples from suspects in the case. By swabbing the inside of a suspect's mouth, authorities get a small sample of saliva and DNA.

For a decisive match between a sample and a piece of DNA evidence, the two strands of DNA have to be identical. Any single variation between sample and evidence will rule out a particular suspect. Forensic scientists decipher the compatibility of DNA samples by:

• Exposing each sample to a series of enzymes to segment each
• Arranging the segments of each according to size (via a process known as electrophoresis)
• Exposing the final arrangement on x-ray film, which renders the sample as a series of black bars (these black bars allow for visual comparison between two samples)

DNA Evidence to Exonerate Convicted Individuals

While DNA evidence was first used to make a conviction in 1988, since then, some who were convicted prior to use of DNA evidence are making use of DNA testing to prove their innocence.

To date, over 190 people have been exonerated through the use of DNA testing. On average, these exonerated individuals served about 12 years in prison before proving their innocence and being released from jail.

Have you or a loved one been wrongfully imprisoned? If so, contact us today to talk to an experienced criminal defense lawyer who will thoroughly evaluate your case and fight to ensure your legal rights are protected.