One of the most important roles that law enforcement officials play in the prosecution of crimes other than the arrest and detention of suspects is the collection, analysis and storage of evidence. Physical evidence ranging from DNA and clothing fibers to footprints cast in cement can help police create a timeline of events before and during a criminal act and to help prosecutors convince a jury of someone’s involvement in a crime.

People often think of physical evidence as the gold standard for criminal cases, but the potential exists for mistakes and contamination to result in inaccurate assumptions about a crime. If the state claims to have substantial physical evidence against you, reviewing the chain of custody for that evidence and challenging its admissibility in court could be a viable criminal defense strategy.

Contamination raises questions for jurors

Evidence in a criminal case must be able to prove someone’s involvement beyond a reasonable doubt. Mismanagement or contamination of evidence could easily lead to reasonable doubts. There’s a reason that police officers keep the public out of crime scenes. They have to prevent the contamination of evidence that could make it difficult if not impossible for them to secure a conviction.

People can wind up tied to a crime scene just because they visited a business or an apartment a day before something bad happens. People could also wind up accused of a crime because evidence gets contaminated, mixed up or lost after police collected it. In order to prevent these sorts of mistakes, there should be very accurate and careful records known as chain of custody records that show who collected the evidence, where it got stored and each time someone tested or reviewed the evidence.

Mistakes or gaps in the chain of custody could mean the evidence is inadmissible

If a careful review of the evidence of the documentation associated with it demonstrates that, for example, a laboratory tested the sample without ever updating the documentation or that the officer who collected the evidence didn’t record their information when they brought in the evidence, that could be sufficient reason to have the evidence declared inadmissible and kept from the jury or judge in the case.

Attacking the credibility and accuracy of physical evidence is one way to protect yourself when facing serious criminal charges, which is one reason why this approach is popular.