Another annoying myth debunked. This time by Erowid:
Loosely defined, entrapment is a situation in which, if not for the actions of the police officer or police informant, the defendant would not have committed the crime. This defense is generally only successful in situations where law enforcement officers create a criminal plan, plant the idea of that plan into an otherwise innocent person’s mind, and then instigate the plan for the purpose of prosecuting the suspect.
The mere presentation of an opportunity or request by an officer that an individual commit a crime does not qualify as entrapment. An officer may engage a citizen in conversation and ask to buy an illegal substance — even if they have no reason to suspect the person of illegal activity.2 They may offer to sell an illegal substance and arrest the buyer after the sale.