Answer: The blood, the door handle, paint, fingerprints,hair,footprints,dust, and if there is a body then they uslly study the body. They can be tested in the CSI and law inforcment, they are tested by the doctors add chemicals and they study it. they study the blood and test how l how long the blood has been there. and by using a magnifyer to see if they missed anything in the blood like dust or dirt or food they study that
Explanation:
I am guessing the answer is number three if I am correct let me know
