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Forensic evidence contamination in your criminal case

Facing criminal charges can be frightening and confusing. You may hear from investigators that they have an overwhelming amount of evidence that pins the crime on you. They may use that supposed evidence to pressure you into confessing to your involvement in the events.

What you may not realize is that the evidence investigators collect from a crime scene may not be as reliable as they say. From the moment the crime occurs until prosecutors present the evidence in court, contamination can corrupt evidence in numerous ways, placing your freedom on the line.

Crime scene contamination

Few crime scenes remain pristine while police collect evidence. Investigators themselves may contaminate evidence if they do not use proper protocol. Nevertheless, they may attempt to use that evidence against you to convict you of a crime. Some ways in which crime scene evidence can easily become contaminated include these:

  • People coming in and out of the area leaving DNA before the crime even occurs
  • People disturbing the crime scene before police arrive, especially if the crime occurs outdoors
  • The environment, such as wind, rain, heat or cold, destroying or diluting evidence like blood or fingerprints
  • Crime scene equipment that investigators do not properly clean and sterilize between crime scenes, leading to cross-contamination
  • Investigators who fail to wear protective clothing -- such as suits, masks and gloves -- or fail to respect the decontamination zone, depositing DNA or other trace evidence from one scene to another
  • Investigators who do not use new, sterile containers or follow proper protocol for collecting and packaging evidence
  • Sun or heat destroying evidence such as blood that officers do not protect during transport
  • Investigators who do not follow the chain of custody, inadvertently mixing up samples

Crime labs are notorious for their sloppy work. It is not unusual for lab workers to lose, mislabel or mix up samples during the testing phase. Additionally, forensic analysts often reuse equipment when testing samples, potentially contaminating the evidence police collected in your case. Nevertheless, these experts may come to the stand and testify that the evidence conclusively implicates you in the crime. Forensic evidence is powerful in the eyes of a jury.

Having a strong criminal defense is critical for disputing forensic evidence. A skilled attorney can challenge the evidence, the process investigators used for collecting and transporting it, and the methods of testing. If you are facing criminal charges, you do not have to feel defeated by the evidence investigators claim to have against you.

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John M. Petruzzi, Attorney at Law
4900 Woodway Drive, Suite 745
Houston, Texas 77056

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Phone: 713-581-1789
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