@nony - I was a juror once at a murder trial. The defense attorney argued that some of the crime scene forensics had been compromised because it had been improperly handled.
It was amazing how they were able to point out the most minute faults in evidence collection, which left doubts in the minds of the jurors as to whether there had been tampering with the evidence.
I don’t believe there was, but other jurors did. You can’t afford to mess up if you want to become a crime scene investigator. If you do, you basically hand the defense its strongest argument.