Deoxyribonucleic acid, or DNA, is often used as important evidence by prosecutors in criminal trials. DNA is a set of molecules that are found inside the human body.
Similar to fingerprints, each individual in the work has a unique and different DNA profile. Because every individual’s DNA is different, a DNA match can be used by prosecutors to prove to a jury that the individual who is facing criminal charges is most likely the individual who committed the crime.
A perpetrator can unknowingly leave behind DNA at a crime scene that can later be discovered, tested, and analyzed by investigators. DNA can be found in many different locations, including:
- Skin cells; and
- Bodily fluids, for example, semen.
Examples of the types of crime scenes where DNA is commonly found includes places where violent crimes occurred, such as:
- Kidnapping; and
- Other incidents that involve physical confrontations.
DNA testing or sampling is used to identify the identity of an unknown individual. Although it is commonly used to identify a criminal suspect, it is also used in other areas of law, for example, paternity testing.
DNA sampling works by extracting a sample of DNA from an individual who is under investigation. A sample can be obtained using a variety of methods, including swab samples that are obtained from the inside of the cheek or bodily fluid samples, such as blood.
A DNA sample is taken directly from the individual in question and compared to any known samples, such as those collected at a crime scene. These samples can be compared to DNA samples that were obtained from other sources of evidence, such as blood stains or strands of hair that were found at a crime scene.
If the two samples match, it can be used as evidence of guilt during prosecution. The reliability of DNA testing may be subject to debate, although it is generally believed to be highly accurate.
DNA collection laws may vary by state, so it is important to consult with an attorney if there are any questions related to this issue.
How Is it Used in Criminal Prosecutions?
If the DNA of a suspect is found at a crime scene, law enforcement officials and scientists can access a national DNA database that is filled with DNA samples taken from criminal offenders. This DNA database, the Combined DNA Index System (CODIS), is used to compare a suspect’s DNA to the DNA of hundreds of thousands of convicted criminals.
This process is sometimes referred to as DNA profiling. If a DNA match is found in the database, the prosecution can use this information as evidence to attempt to prove that the suspect on trial is the individual who committed the criminal act.
It is important to note that finding DNA at a crime scene does not always lead law enforcement to the individual who is guilty of committing the crime. In certain cases, an individual’s DNA may be found at a crime scene, but that individual was not involved in committing the offense.
In some cases, the DNA sample may be incomplete, damaged by age or weather, or mishandled by investigators. In these types of cases, the DNA sample will be considered inconclusive evidence and may not be used by criminal prosecutors.
How Can Law Enforcement Officials Get Samples of a Suspect’s DNA?
Law enforcement officials may be able to obtain samples of a suspect’s DNA if there has not been a suspect located in the national DNA database. In certain states, individuals who have been convicted of certain crimes are required by law to provide samples of their DNA.
This requirement is referred to as mandatory DNA sampling. The laws governing mandatory DNA sampling vary by state and by crime.
The types of crimes that usually require mandatory DNA sampling are typically violent crimes and felonies, including murder and rape. In other situations, a suspect may give law enforcement permission to take a DNA sample.
A DNA sample is usually taken from a suspect in the form of a blood draw or saliva swab. If the suspect is eventually found not guilty of the crime, they can request that their DNA be removed from the national DNA database.
If the suspect refuses to provide a DNA sample, law enforcement officials may be able to obtain a sample by collecting an everyday item that was used by the suspect. For example, DNA can be collected by taking saliva samples from used cups or hair and skin samples from hair brushes or razors.
Is DNA Testing Mandatory in a Criminal Investigation?
Currently, there is mandatory DNA collection in all fifty states for certain felony crimes, mostly sexual assaults and homicides. In 47 states, DNA samples are taken from all convicted felons.
In addition, some states have implemented mandatory DNA testing for juvenile offenders. In certain states, any suspect who is arrested is required to undergo DNA testing.
For example, in California, any suspect who is arrested for a felony must submit to testing. Some states may require DNA sampling for certain misdemeanor crimes as well.
Due to the fact that a suspect may be required to submit to DNA testing before they are found guilty, the constitutionality of DNA testing is often a topic of debate. Many individuals believe that mandatory DNA testing is an invasion of privacy, especially the types of sampling that require some type of bodily intrusion, for example, drawing blood.
Because of this, DNA testing requirements may vary by state. Although DNA testing is typically used to prosecute a suspect, it may also be used for their defense and exoneration. For example, a defendant may offer the DNA sample as evidence that they did not commit the crime.
What Is the Combined DNA Index System (CODIS)?
The Combined DNA Index System, CODIS, is a type of DNA database. It uses computer systems to store DNA profiles of individuals that are generated by crime laboratories.
These DNA profiles may be connected with local, state, or federal criminal violations. CODIS provides authorities with the ability to browse the database to identify suspects.
Therefore, if an individual has previously submitted to DNA testing, a record of their DNA profile is likely held in CODIS.
Can I Have My DNA Profile Removed from a DNA Database?
In certain situations, an individual may petition to have their DNA sample or profile removed from a DNA identification database. This is typically permitted if the individual was cleared of criminal charges or is seeking to have their criminal record expunged.
For example, an individual who is in the process of expunging a conviction in Arizona may request to have their DNA profile removed from the Arizona database systems. This request to have their DNA profiles removed may, in many cases, be submitted along with the expungement petition.
Do I Need a Lawyer for Issues with DNA Sampling?
DNA sampling in criminal investigations has been a widely debated issue ever since its use began. If you have any issues, questions, or concerns related to DNA sampling, it may be helpful to consult with a criminal lawyer for advice.
Your lawyer can explain the DNA sampling laws in your state as well as your rights. In addition, your lawyer can determine whether DNA testing is appropriate in your situation and whether it will serve to help your case.
If you have been convicted of a crime and are seeking an expungement of your record, your lawyer can assist you with those requests and ensure they are completed.