Chain of Custody Envelope

Why is it important to strictly monitor who interacts with evidence?

This envelope details who viewed this evidentiary tape during the case and where. The tape detailed the exact times Timothy McVeigh visited Equity Standard Numismatics – located in Wichita, Kansas, a store that exchanges money for gold and coins. McVeigh was seen visiting between October 13 and 24, 1994. How evidence is handled during a case is strictly monitored.