Since making its courtroom debut in the mid-1980s, DNA evidence has become an integral component in thousands of cases throughout the United States. Attorneys and juries alike generally consider DNA evidence to be immensely reliable. According to a 2015 Gallop poll, 58% of people viewed DNA evidence as “very reliable.”
But despite the clear advantages DNA evidence offers, there remain weaknesses with DNA testing. This type of evidence can be vulnerable to mistakes and mishandling.
The following are the most common errors related to DNA evidence:
- DNA can be transferred accidentally. In a California murder case, police discovered traces of DNA under the victim’s nails and the DNA matched an individual with a criminal record. However, the suspect in question had been hospitalized when the murder occurred. In conclusion, the paramedics had transported the suspect from a motor vehicle accident to the hospital, and then had gone to the crime scene without washing their hands.
- Mishandling DNA evidence. There are many instances where police had not followed proper protocol for storing evidence. In the Netflix series “How to Make a Murderer,” police found DNA from the defendant that connected him to the crime scene where a photographer had been murdered. But law enforcement officials could not say whether or not they had followed procedures for handling evidence. The defense had suggested the evidence had been tampered with and the suspect’s DNA had been planted on the crime scene.
- Timing and contamination. If the victim and the suspect had an ongoing relationship, the DNA may have been left in the days before---and not when---the crime occurred. It is difficult to determine exactly when biological material was left. When there is some time between when the crime is committed to when the police discover traces of biological material, the material in questions may be contaminated by other people by then.
As you can see, DNA evidence is not always right. In regards to criminal defense, that could be the difference between freedom and life behind bars.