I remember there was a big story here about 15 years ago that involved police corruption in a murder case. Apparently a crooked cop had tampered with an evidence log to make it look like a piece of evidence hadn't been removed. The evidence was integral to the case. It was a pretty clumsy operation because the cop was caught and the defendant was found guilty. But this just goes to show that no system is foolproof. Even an evidence log can be tampered with when it is in the control of the police.