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How reliable is DNA evidence?

On Behalf of | Dec 8, 2022 | Criminal Defense

The police and prosecutors are fond of DNA evidence. If they find traces of your DNA on something, they may believe it proves you committed the crime.

Yet, it is not as clear-cut as they might suggest. Here are some of its weaknesses:

2 example of DNA cross-contamination

DNA evidence can be easily transferred between people. Cross-contamination is a serious issue and has led to innocent people being convicted. 

For example, you could stand in a crowded train carriage and, as the train jolts, your head rubs against a person’s coat, leaving hair from your head on their coat. After they leave the train, they commit a crime, and your hair drops off their coat at the crime scene. 

When the forensic team comes along, they find the hair, test it for DNA and trace it to you. The prosecution presents it as evidence that you committed the crime.

Another example may occur if you are walking through a local park when you see a rusty knife on the ground. You pick it up to look, then toss it into the nearest bin to prevent anyone from treading on it. 

What you do not realize is someone was stabbed with that knife a few weeks ago. The police find it and send it for testing. It comes back with only your DNA evidence on it as the attacker used gloves so as not to leave their DNA on it. The police refuse to believe that you were not the attacker.

Getting legal help from someone who understands the possible flaws of DNA evidence will be crucial if you face criminal charges due to traces of your DNA being found.