"Innocent defendants may plead guilty in return for a shorter sentence to avoid the risk of a much longer one. A prosecutor can credibly threaten a middle-aged man that he will die in a cell unless he gives evidence against his boss. This is unfair, complains Harvey Silverglate, the author of “Three Felonies a Day: How the Feds Target the Innocent”. If a defence lawyer offers a witness money to testify that his client is innocent, that is bribery. But a prosecutor can legally offer something of far greater value—his freedom—to a witness who says the opposite. The potential for wrongful convictions is obvious."