The Importance of DNA in Sexual Assault Cases

Source of this information: RAINN (Rape, Abuse & Incest National Network) is the nation’s largest anti-sexual violence organization. RAINN created and operates the National Sexual Assault Hotline (800.656.HOPE, y in partnership with more than 1,000 local sexual assault service providers across the country and operates the DoD Safe Helpline for the Department of Defense. RAINN also carries out programs to prevent sexual violence, help survivors, and ensure that perpetrators are brought to justice.

When law enforcement investigates a case of sexual violence, DNA evidence can make or break the outcome. DNA evidence has become a routine part of investigating and prosecuting all types of crimes. It is often an important tool in achieving justice for survivors of sexual assault.

What’s the benefit of having a sexual assault forensic exam?

  • Increases likelihood of identifying the perpetrator. Analyzing DNA samples allows forensic scientists to compare the profile of the perpetrator against a large database with thousands of profiles run by the FBI called CODIS, the Combined DNA Index System.
  • Increases likelihood of holding perpetrators accountable. If the state presses charges against a perpetrator, DNA evidence will likely carry weight in court. Many cases of sexual violence rely on first hand accounts and other evidence that leaves room for interpretation. DNA evidence helps build a stronger case against the perpetrator.
  • Prevents future sexual assaults from occurring. Perpetrators of violence tend to be serial criminals, and sexual violence tends to be a serial crime. When you agree to a sexual assault forensic exam and DNA testing, you increase the chances of taking the perpetrator off the streets and preventing any future instances of sexual violence. Even if the perpetrator is not prosecuted, their DNA will be added to the database, making it easier to be connect the perpetrator to a crime in the future.

What is DNA?

DNA is the material found in cells that determines characteristics such as eye, hair, and skin color. Each person’s DNA is different, except for identical twins. This means that DNA can be used to accurately identify a perpetrator, similar to the way we use fingerprints. DNA evidence can be collected from blood, saliva, sweat, urine, skin tissue, and semen. That’s why it’s important to try to avoid bathing, cleaning your fingernails, or urinating until after a sexual assault forensic exam has been performed.

Where can DNA evidence be found?

Trained investigators may look for DNA evidence at locations that are relevant to the case, such as the scene where the assault took place. DNA evidence can also be collected from the body and clothes of the person who survived the assault during sexual assault forensic exam. The exam is performed by a Sexual Assault Nurse Examiner (SANE) or another trained medical professional. In addition, DNA may also be collected from anyone who was known to have been at the crime scene, including the responding officer, any witnesses, as well as anyone you may have had consensual intercourse with in the 72 hours prior.

What happens to DNA evidence?

Once DNA is collected, there is a protocol for how the evidence is handled and used in an investigation. The evidence will be provided to law enforcement who may send it to a crime lab. The lab will analyze the material and develop DNA profiles that are unique to a specific person. The lab works with law enforcement officials to compare these profiles to the DNA of potential suspects. If the perpetrator is unknown, they may compare the DNA profile against a large database run by the FBI called CODIS, the Combined DNA Index System. This way, they can identify suspects that the victim doesn’t know or isn’t familiar with.

Law enforcement may not be able to locate and arrest the suspect if the legal time limit for pressing charges has passed. This is period of time is called the statute of limitations, and it varies by state, type crime, age of the victim, and other factors. Check out the statutes of limitations in your state using RAINN’s State Law Database.


2 replies

  1. but surely DNA tests would need to be done immediately. How is it useful when reports or accusations are raised years later (like in Prince Andrew’s case for instance).?

  2. DNA tests only get you so far. The vast majority of sexual assault victims are assaulted by men they know- husband, boyfriend, ex-partner, friend, colleague… In these cases DNA doesn’t mean a great deal as the perpetrator simply says they had consensual sex.

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