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
On the other hand, the prosecutor may wish to maintain a high conviction rate and avoid losing high-profile trials; thus, settling a case by plea bargain may further his interests, even if the resulting sentence would not effectively deter crime. As many crimes have very narrow sentencing bands, a prosecutor often has scope to propose whatever degree of "discounted" charges, or substitution of misdemeanor rather than felony charges, to whatever extent they believe would incentivise a defendant to make a guilty plea and accept a speedy conviction, regardless of actual guilt.