I was just remembering a movie scene where 2 undercover cops knock on a man's door asking to buy drugs and and he sells it to them. In the end he is arrested and convicted. I'm no expert but I thought entrapment usually occurred when the illegal activity it pushed or initiated by the law enforcement offer so would this situation be entrapment? On a broader note, I know the often fine line between entrapment and a legal sting operations is widely debated to what, fundamentally, distinguishes a legitimate sting from unfair entrapment?
Entrapment is law enforcement tricking someone into committing a crime they were not already willing to do. It has two parts: 1) police inducement and 2) lack of predisposition.
There are two key elements:
Government inducement - Police must have persuaded, pressured, or lured the defendant into the crime through more than just providing an opportunity. Repeated requests, appeals to sympathy, or large financial rewards can count as inducement. Simply asking to buy drugs likely does not qualify.
Lack of predisposition - The defendant must not have been willing or planning to commit the crime prior to the police inducement. If the defendant already intended to commit the crime, entrapment likely does not apply.
The difference between a legal sting and entrapment depends on facts of each case. In a legal sting, police provide an opportunity for someone already willing to commit a crime. In entrapment, police pressure an unwilling person into a crime they otherwise would not commit.
The scenario you described could potentially be entrapment based on the level of inducement and the defendant's lack of predisposition. However, more details would be needed to determine for sure. Undercover cops simply asking to buy drugs is likely not sufficient inducement to constitute entrapment.