Crime Scene Scenario – Mistakes or No Mistakes?

Criminalist Pete Evett is collecting fiber evidence from a murder scene. He notices fibers on the victim’s shirt and trousers, so he places both of these items of clothing in a plastic bag. He also sees fibers on a sheet near the victim, so he balls up the sheet and places it in a separate plastic bag. Noticing fibers adhering to the window sill from which the attacker gained entrance, Pete carefully removes them with his fingers and places them in a regular envelope. What mistakes, if any, did Pete make while collecting this evidence?