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Evidence contamination and how it happens

On Behalf of | Dec 15, 2022 | Criminal Defense

The chain of command for evidence in a criminal case is only one component of ensuring the evidence is not contaminated. Unfortunately, there are times when laboratory personnel or law enforcement officials make mistakes and contaminate evidence.

This can greatly influence a criminal case. If the contamination is serious enough, the judge may exclude the evidence from the case.

DNA evidence contamination

DNA evidence is extremely important in almost every criminal case. When contamination occurs, the entire focus of the case may change. The National Institute of Justice provides some tips on how to avoid contamination of DNA for laboratory workers.

  • Always wear gloves and change them regularly
  • Throw away disposable instruments when changing samples
  • Do not touch the area where the DNA is
  • Never cough, sneeze or talk around evidence
  • Before packaging evidence, it should be air-dried
  • Place evidence in new envelopes or paper bags rather than plastic bags and never use staples

These tips can help protect the evidence while at the lab, but storage and transportation often create issues also. Always store evidence at room temperature and keep it dry. Once evidence is in an envelope or paper bag, label, seal and transport it in the appropriate way.

Chain of command

Document the chain of command to determine who handled the evidence since collection and why. This is important because if anyone tampers or misplaces evidence, the documentation determines where that happened and if it was intentional or accidental.

Anyone charged with a crime deserves to have a fair case brought against them with a fair chance to prove their innocence. Tampering with or mishandling evidence greatly influences the fairness of the case brought against the accused.