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
[P]lea bargains are just as likely in strong and weak cases. Prosecutors only need to adjust the offer to the probability of conviction in order to reach an agreement. Thus, weaker cases result in more lenient plea bargains, and stronger ones in relative harshness, but both result in an agreement. [... W]hen the case is weak, the parties must rely on charge bargaining ... But [charge bargaining] is hardly an obstacle. Charge bargaining in weak cases is not the exception; it is the norm all around the country. Thus, even if the evidence against innocent defendants is, on average, weaker, the likelihood of plea bargains is not dependent on guilt.