When police induce a previously-innocent person to commit a criminal offense, the police have engaged in "entrapment." Entrapment is a defense to a criminal prosecution, even though a non-governmental actor offering an inducement of the same sort would not provide an excuse to the very same conduct by the defendant. If the government repeatedly and relentlessly tempts a person to sell drugs until the target finally does so, the target may prevail against a criminal prosecution with an entrapment defense. The basic rationale of this defense is not that the defendant did no wrong, but rather that the crime came from the government. We are thus more disturbed by the government's role in creating a crime and a criminal where there were none before, than we are by the criminal conduct itself, and thus we excuse the latter to deter and penalize the former.
When the government asks a baseball player questions about his own and his teammates' use of performance-enhancing drugs, it engages in a species of entrapment (though not one recognized as a common law defense to crime). The government knows that performance-enhancing drugs have become quite common in baseball, but its investigators and prosecutors have a difficult time gathering specific and accurate information on the subject, because players are predictably reluctant to speak openly. Understanding this state of affairs, the government conducts numerous interviews with players and asks questions, the answers to which are likely to be unhelpful and downright false. Armed with provable falsehoods, government officials no longer need to find out actual facts about drug use. All the government has to do is show that suspected baseball players lied.