An Officer Has Made a Lawful Arrest of a Suspect

An officer has made a lawful arrest of a suspect in the suspect's home based on a warrant for the crime of fraudulent and worthless check writing. While waiting for the arrestee to phone his wife, the officer notices an envelope lying on the kitchen table. The officer opens the envelope and discovers several checks, which the officer recognizes as forgeries. Which requirement of the plain view doctrine is not fulfilled (or has been violated) ?

A) prior valid intrusion
B) inadvertent discovery
C) probable cause item subject to seizure
D) no unreasonable intrusion on privacy