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5 Key Aspects to Challenge With DNA Evidence
DNA evidence was first used in a criminal case in the 1980s, and while the technology was more cumbersome then, it has advanced at lightning speed. Today, DNA evidence is often used as a cornerstone for cases against those charged with violent crimes, such as rape or murder. The general principle behind DNA evidence is that everyone — except identical twins — has a unique DNA profile. We also leave some of this DNA behind in bodily fluids and sometimes even the items we touch. If DNA evidence is left at a scene and it matches the DNA profile of the defendant, it can be a challenging piece of evidence to overcome. However, it is possible, and there are various strategies an attorney can use to do so.
1. How the DNA Was Collected
DNA evidence is highly susceptible to contamination, so extreme caution and precision must be used when the DNA is collected. Sterile collection procedures that meet current forensic standards are critical to ensure the sample’s integrity. If a crime scene technician didn’t use proper protective equipment, it could result in a contaminated — and, therefore, inaccurate sample. An attorney can attempt to challenge DNA evidence by pointing out these issues or arguing that other factors, such as the environmental conditions at the collection site, make the sample unusable.
In some cases, DNA is collected directly from the defendant when they are identified as a person of interest. Investigators generally need the defendant’s consent or a warrant to collect DNA, but a few exceptions exist. Officers generally can collect the sample without a warrant if the defendant discarded the DNA, such as drinking out of a cup and then throwing it in the trash.
2. Chain of Custody
Once the DNA is collected, proper procedures must be followed to ensure the sample isn’t contaminated or otherwise altered from the collection site to the lab. This is referred to as the chain of custody. Officers must have documentation of the sample from collection to analysis, and every person who handled the evidence must be identified and recorded. If the evidence was left unattended at any point or there are gaps or inconsistencies in the chain of custody, it could be grounds to challenge the evidence and potentially have it ruled as inadmissible in court.
3. Lab Handling, Storing, and Analysis Procedures
When evidence is sent to a lab for analysis, specific procedures must be followed to ensure the integrity of the sample and the result. If there are issues with the packaging, labeling, or sealing of the evidence at any point, the DNA may be unusable due to tampering concerns.
Lab technicians must be trained on the proper testing methods, and equipment must be regularly maintained and calibrated to ensure it works correctly. Even something as small as an issue with the sample storage conditions, such as the temperature being too hot or too cold or the sample being stored in the wrong type of container, can be something an attorney can use to challenge the DNA evidence and a result that ties the defendant to the crime.
4. The Quality of the Sample
While the technology used for DNA sampling and analysis is ever-evolving, it does have some limitations. For example, it’s generally easier to get DNA from a body fluid sample than from something the perpetrator touched. The lab also needs enough of the DNA to be able to perform an analysis. If the sample size is too small, it could result in an inaccurate analysis or not being able to analyze the sample at all.
It’s also possible for a sample from a crime scene to include a mixed DNA profile, meaning there is DNA present from multiple people. These kinds of samples are common in touch DNA and in high-traffic environments. The more people who have been through the scene, the more likely it is for the sample to contain multiple DNA profiles. This can make it more challenging to isolate the individual contributors, especially if they are related and already share some DNA.
5. Why the DNA Was Present
In some cases, an attorney may focus less on challenging the presence of the DNA itself and, instead, concentrate on providing an alternative explanation for why the DNA was present. For example, if the DNA was found in the victim’s home but the defendant was a close friend or family member who visited the house multiple times in the days before the incident, this could explain why their DNA is present at the scene. DNA evidence that is collected from common areas or shared public surfaces can be challenging to connect to the crime itself because there can be many reasons the defendant’s DNA is present.
In most cases, the prosecution needs more than just DNA evidence. They also have to tie that evidence to the crime. Working with a defense attorney to challenge DNA evidence means that you have someone on your side who is able to undermine this connection and potentially introduce reasonable doubt for the jury.
DNA can be persuasive evidence, but it’s not impossible to overcome. Whether it’s challenging the credibility of the evidence itself or filing a motion to dismiss the evidence, the team at The Defense Group can help you present a strong defense in a violent crime case, even when DNA evidence is part of the prosecution’s case. Call 407-743-8430 to schedule a time to talk with a defense attorney at The Defense Group.
