Tom and William got off of work at 5:00 pm and started drinking at Tom's house. After drinking many beers the two men began arguing verbally with each other over pay. William picked up a heavy glass ash tray and struck Tom over the head with it. Tom later died from a traumatic brain injury. During the collection of evidence Officer Smith cut his finger on some broken glass as he was placing the bloody ash tray into an evidence bag. What is this known as?
A) Proactive policing.
B) A boo boo.
C) Contamination.
D) Chain of custody.