The basic rule of entrapment (California Penal Code 647a) is that to qualify as a defense, the police have to actually plant the idea of the crime in your head. They must do this by engaging in some type of enticement. One of the ways this is done is to make the reward so lucrative the police essentially overcome your free will. This can also be accomplished if the defendant is in an especially vulnerable position. Entrapment can be a complete defense to charges of wrongdoing.
This will be easier to understand by looking at an example. In the early 1980’s, James DeLorean, the man who invented the DeLorean car was in danger of losing his automobile company because he was in deep financial trouble. The FBI and Drug Enforcement officials devised a sting operation in which informants and undercover FBI agents came to DeLorean and wanted him to sell 55 pounds of cocaine. DeLorean had no prior record and no history of drug sales.
Lawyers for DeLorean argued that he was in an especially vulnerable position in that his company was on the brink of disaster. In addition, they argued, the agents offered an amount of money that was so huge that no reasonable person would be able to turn it down. DeLorean, they argued, never had any intention of selling drugs until the FBI agents planted the idea in his head. A jury agreed with the defense and acquitted DeLorean of the charges. This was reported in Time Magazine.