Call for Consultation (337) 366-8994
Call for Consultation (337) 366-8994
DNA evidence is considered the gold standard in criminal investigations. It’s used to link suspects to crime scenes and secure convictions. While DNA analysis can be a powerful tool, it is far from infallible.
Mistakes in collection, handling, and interpretation can lead to wrongful accusations and even wrongful convictions.
Understanding the limitations of DNA evidence is important. DNA does not tell the full story despite its accuracy. It cannot determine when or how it was left at a crime scene. In other words, DNA identification cannot explain “time, place, or circumstances” for how DNA can be on a piece of evidence.
This is why a strong legal defense is essential when DNA evidence is used against you.
Charged with a crime involving DNA evidence? The Ikerd Law Firm can challenge faulty evidence and protect your rights. Call (337) 366-8994 for a consultation.
Popular crime shows like CSI and Law & Order have created unrealistic expectations about DNA evidence. This is known as the “CSI Effect”. It’s where jurors believe DNA is always available, always accurate, and always the deciding factor in a case.
DNA evidence is just one piece of a much larger puzzle. A flawed understanding of its reliability can lead jurors to overestimate its value. It can make it harder for defendants to receive a fair trial.
Many people mistakenly believe that a DNA “match” means absolute proof of guilt. DNA testing is based on probabilities. A reported match might mean there’s a 1 in 10,000 chance that the DNA belongs to someone else. Or a 1 in billion chance, depending on the test. The accuracy of these statistics depends on the quality of the sample and the methods used in testing.
DNA evidence does not explain time, place, or circumstances. A person’s DNA at a crime scene does not prove they committed a crime. It only proves that their DNA was found there. There may be entirely innocent reasons why DNA was left behind.
DNA can easily be contaminated at any stage—from the crime scene to the lab. Contamination happens when foreign DNA mixes with a sample. It makes it difficult to determine who the actual contributor is of the DNA.
Real-world cases have shown how contamination leads to false accusations. A DNA sample from a crime scene in a city matched multiple women across different locations within that city. Investigators later discovered that the DNA belonged to a factory worker who had unknowingly contaminated swabs before they were sent to police departments.
For DNA evidence to be reliable, it must be properly documented and tracked from the moment it is collected. Any gaps or mishandling in the “chain of custody” can result in evidence being inadmissible in court.
If samples are mislabeled, stored incorrectly, or lost for periods of time, the integrity of the evidence is compromised. Defense attorneys frequently challenge DNA evidence when errors in the chain of custody are found.
Mislabeling and tracking mistakes happen more often than people realize. A simple clerical error (like switching two vials) can mean an innocent person is linked to a crime they had nothing to do with. These errors highlight the need for independent review and rigorous cross-examination of DNA analysts in court.
DNA degrades over time due to environmental conditions like heat, moisture, and light exposure. When degraded samples are tested, they can produce unreliable or partial results that make identifying the correct individual difficult.
A partial DNA match increases the risk of misidentification. Fewer genetic markers are available for comparison. This can wrongly implicate someone who shares similar genetic traits with the actual contributor.
Identifying individual contributors becomes difficult when multiple people’s DNA is present on an object or at a crime scene.
LCN DNA testing amplifies tiny amounts of genetic material to make identification possible. While this can be useful, it also increases the risk of false positives because of contamination or lab errors.
LCN testing is often considered less reliable than traditional DNA analysis because of its sensitivity.
Some courts have even ruled that LCN results are too unreliable to be admissible.
Touch DNA refers to DNA left behind when a person touches an object. Touch DNA does not prove direct contact. Even microscopic amounts of skin cells are transferred from one person to the next.
If someone shakes hands with a person who later commits a crime, their DNA could be transferred to a weapon or other object at the scene despite never being present themselves.
DNA analysis is performed by humans. And human error is always a possibility. Mistakes such as cross-contamination, sample mislabeling, and procedural shortcuts can lead to incorrect conclusions.
DNA analysts sometimes overstate the reliability of test results. One common issue is “probabilistic genotyping,” where software programs (such as TrueAllele or STRMix) generate statistical probabilities of a match.
These programs rely on assumptions that may not always be accurate. But their results are often presented as scientific facts in court.
DNA testing requires strict protocols. This includes regular equipment calibration and thorough documentation. The accuracy of results suffers when labs cut corners.
DNA matches are not absolute—they are based on probability. Multiple people could be a match if a test says there’s a 1 in 10,000 chance that another person in the population shares the same DNA markers
Many jurors are unaware of the limitations of DNA testing. Prosecutors may present DNA as undeniable proof. This can lead jurors to ignore other weaknesses in the case. Defense attorneys work to educate jurors on the fallibility of DNA and ensure they thoroughly check the evidence.
DNA evidence does not show when it was deposited or under what circumstances. Someone’s DNA at a crime scene does not mean they were there during the crime. This is a critical argument defense attorneys use to cast doubt on the prosecution’s case.
A skilled defense attorney will examine the:
Defense attorneys often request independent DNA analysis to verify or challenge the prosecution’s findings. Third-party experts can uncover errors or limitations that law enforcement overlooked.
Experienced defense attorneys question forensic experts on lab procedures, statistical probabilities, and possible contamination. Exposing inconsistencies in expert testimony can weaken the prosecution’s reliance on DNA evidence.
DNA from genealogy databases like 23andMe and Ancestry.com has been used to identify suspects through relatives. While this can help solve cases, it raises concerns about privacy and wrongful identification.
Law enforcement now uses familial DNA searches to track down relatives of suspects. This practice can mistakenly implicate innocent people based on distant genetic similarities.
While new methods in DNA testing continue to emerge, they often lack validation. Relying on unproven technology can lead to wrongful convictions.
DNA evidence is often portrayed as undeniable proof. If you are facing criminal charges based on DNA evidence, do not assume it is beyond challenge.
A skilled defense attorney can scrutinize the evidence, expose errors, and fight for your rights. DNA is just one piece of circumstantial evidence—not the final word on guilt or innocence.
