The following is taken from the case notes of Chief Inspector Tiffany Terrier, a veteran of crime scene detection.
Detection and interrogation techniques
Step one. Sniff it. Sniff it some more.
Step two. Ask yourself…
A) Can I eat it?
If no, go to…
B). Can I wee on it?
Usually yes, if however this isn't possible go to…
C). Can I roll in it?
Yes, case solved.