Misprision is a noun that means the neglect or wrong performance of official duty.
The Latin word prehendere (PREN dare ay) means ‘to seize’ or ‘to take.’ As the word drifted through Middle English, the prefix MIS was added and the word evolved into our word of the day. In addition to its most common meaning, Misprision may be used in a few legal contexts like: ‘concealment of treason or felony by one who is not a participant in the treason or felony’ or ‘seditious conduct against the government or courts.’
When that security guard followed that suspicious man to his car, he may have thought he was helping out, but really he was engaging in an act of misprision. His job was simply to report unusual behavior.