Plea bargaining in the United States
The constitutionality of plea bargaining was established by "Brady v. United States" in 1970, although the Supreme Court warned that plea incentives which were sufficiently large or coercive as to over-rule defendants' abilities to act freely, or used in a manner giving rise to a significant number of innocent people pleading guilty, might be prohibited or lead to concerns over constitutionality. "Santobello v. New York" added that when plea bargains are broken, legal remedies exist.
Plea bargain
Largely unique to the Canadian justice system is that further negotiations concerning the final disposition of a criminal case may also arise even after a sentence has been passed. This is because in Canada the Crown has (by common law standards) a very broad right to appeal acquittals, and also a right to appeal for harsher sentences except in cases where the sentence imposed was maximum allowed. Therefore, in Canada, after sentencing the defence sometimes has an incentive to try and persuade the Crown to not appeal a case, in exchange for the defence also declining to appeal. While, strictly speaking, this is not plea bargaining, it is done for largely the same reasons.