The existence of DNA evidence in a sexual assault case, or even more important, the lack of such evidence, can greatly impact the outcome of a criminal or civil trial. However, despite what is often portrayed in television shows, DNA is not always considered conclusive proof of a rape or sexual assault. DNA evidence can also be used to prove innocence and often is key to winning a case and/or reducing a sentence.
Knowing how to effectively use DNA evidence at trial is difficult. Anyone who has been accused of rape or sexual assault may want to consult a sex crimes defense attorney who is highly experienced in this area and can ensure any such evidence is properly presented or challenged.
In this article, we’ll examine the types of DNA evidence often found in rape and sexual assault cases and how the science behind them can be used toward a defense of such crimes.
What is DNA evidence?
DNA stands for deoxyribonucleic acid. Almost all living organisms contain DNA material. It is a self-replicating element of our body’s chromosomes and carries our unique genetic information. Every person in the world has different DNA, except identical twins.
There are two kinds of DNA. The first is found in bodily fluids, such as semen, saliva, and blood. The second type, epithelial DNA, comes from skin cells. DNA can be used to help identify and confirm the presence of a person in a specific location or their interaction with another.
In cases of sexual assault, DNA material is often gathered at the scene of a crime where bodily fluids may be present. It is also often obtained from the body and clothing of the victim. To rule out the presence of third-party DNA – from people who may have inadvertently left DNA at the scene – law enforcement personnel will likely take DNA samples from officers, friends and family, witnesses, and others the victim may have engaged in sexual conduct with within 24 hours of the crime.
DNA retrieval from the body of a victim by medical personnel typically occurs soon after the alleged crime happens. Sexual Assault Nurse Examiners (SANE) are trained to complete “rape kits”, wherein they use medical tools to gather DNA samples. It’s important for any DNA evidence not to be disturbed until the victim can be examined, so victims are often advised not to use the bathroom, bathe, change clothes or clean their fingernails until they visit a SANE.
For DNA to be accepted as authoritative evidence in a sex crime trial, it must be gathered properly by trained investigators, and the gathered evidence must follow a proper chain of custody to maintain its integrity and reliability.
How is DNA used as evidence in a sexual assault trial?
Forensic scientists can analyze DNA and use the profile to attempt to match the results to offender records in the FBI’s Combined DNA Index System (CODIS). This is useful when the identity of a perpetrator is unknown. DNA analysis is also convenient for attempting to match DNA with a specific person who has been accused. As CODIS has only formally existed since 1994, if the suspect is not listed in CODIS, the court can order a DNA sample to be taken.
In general, prosecuting attorneys must prove two facts to successfully convict someone of rape or sexual assault: 1) there was sex between the accused and the accuser; and 2) it was not consensual sex. DNA can only be used to help prove the first of the two elements, but it can also be used to rule out the presence of an accused person or at least create doubt.
The hard-scientific evidence provided by DNA can help verify facts that are often only supported by witness interviews and other circumstantial or biased evidence. However, in many sexual assault cases, the evidence presented is not conclusive or leaves room for interpretation.
Because of the limitations of using DNA as evidence, DNA results are often supplemented with other evidence to secure a conviction. Other evidence sometimes used in concert with DNA evidence includes injuries consistent with sexual assault, phone records, text messages, social media posts or interviews with witnesses.
If it is determined there is no DNA matching the accused, it causes doubt as to (1) whether the assault took place, and (2) whether the accused committed it.
The Problem with DNA
Sometimes DNA evidence is unusable or corrupt if the samples of bodily fluids have not been collected or transferred properly. In extreme cases, DNA evidence has been falsified by law enforcement officers to ensure a conviction.
Even if the integrity of samples can be confirmed, DNA evidence can only support certain facts. If DNA belonging to the accused person is found at the scene of the crime or on the body of the victim, it establishes the accused and the accuser spent time together. If retrieved from certain parts of the body, it may even prove they had sex, but the DNA itself cannot prove the sex was not consensual.
If DNA of the accused is NOT present, it does not necessarily mean a sexual assault did not take place. In that situation, prosecutors must look for other ways to prove the criminal act. Injuries consistent with sexual assault, for example, might get a jury to consider the possibility that the alleged sexual assault did take place even if DNA isn’t available—especially if there are coordinating injuries on the bodies of both the victim and the accused. However, injuries are not always present, even if an assault did take place.
It is important for a defense attorney to thoroughly explain applicable limitations of DNA analysis to a jury. People who serve as jurors are regular citizens who hear about sexual assault through friends, the news, television shows, or movies. It is common for jurors on sexual assault cases to put too much trust in DNA evidence because they are used to seeing it on TV. This is sometimes called the CSI effect. It is the defense attorney’s job to keep jurors from drawing the wrong conclusions and making unfounded assumptions based upon their own knowledge of DNA evidence.
In addition to these problems with DNA evidence, when a city, state or the federal government prosecutes a sexual assault case, their efforts are narrowly focused on proving that a sex crime DID occur, so analysis can be slanted toward prosecution. The evidence is not always helpful in defending someone who has been falsely accused (i.e., proving a crime did NOT happen). Defense attorneys must find other means of defending the rights of the accused.
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How DNA is Used to Defend Against Rape or Sexual Assault Charges
If an accused person’s DNA is not found at the scene of a crime or on the body of the victim, a defense attorney may successfully convince the court to drop the charges, because this suggests the person could not have been at the scene of the crime, if there is no other reason the DNA evidence might not be present. This is the simplest use of DNA in sexual assault defenses.
Defense becomes more complex when the accused was at the scene of a crime but did not commit the crime. Because sexual assault often involves interaction between people who know each other, it is not unusual to find DNA for the accused at the scene of a crime or on the body of the victim when the accused and victim have some kind of relationship. It’s the prosecution’s job to prove the crime beyond the person’s presence at the scene. Defense is often a matter of getting the court to focus more on the question of whether sex was consensual than on proving the accused was present.
A famous case in which charges were dropped due to the doubt created by DNA evidence involved basketball star Kobe Bryant. In this case, DNA of other people the victim had sex with was gathered at the scene and from the victim’s body. This information was used, in addition to evidence surrounding her injuries, to cast doubt on the claim that sex with Mr. Bryant was not consensual.
No matter what the situation, if you or someone you know has been accused of rape or sexual assault, you may want to contact an experienced sex crimes attorney as soon as possible. As early in the process as an investigative interview, it can be easy to inadvertently provide evidence that can be used against you. Your attorney can help you navigate the challenges of a successful defense.
If you or someone you know has been accused of sexual assault or sexual harassment, call the Berry Law and make an appointment for an experienced sex crimes attorney to hear your story.
