In the 1971 case of Santobello v. New York, the United States Supreme Court ruled that when a plea agreement has been made, it must be fulfilled. The defendant, Santobello, had agreed to plead guilty to a lesser charge in exchange for a lighter sentence recommendation from the prosecutor. However, at sentencing another prosecutor who was not aware of this deal recommended a harsher sentence which was subsequently imposed by the judge. When Santobello appealed on grounds that his plea bargain had not been honored and he should therefore have an opportunity to withdraw his guilty plea or enforce the original agreement's terms; both state courts denied him relief. The Supreme Court reversed these decisions stating that due process requires fairness in securing agreement between an accused and a prosecutor and such mutual commitments must be fulfilled.

In the dissenting opinion for Santobello v. New York, Justice Harry Blackmun argued that the majority's decision to reverse and remand was unnecessary because there were no constitutional violations in this case. He stated that while it is regrettable that a prosecutor did not honor his plea agreement with the defendant, such an action does not necessarily constitute a violation of due process rights under the Fourteenth Amendment. Furthermore, he pointed out that Santobello had received a fair trial and was convicted by an impartial jury; thus, any error made during plea negotiations did not affect his right to a fair trial or sentencing hearing. Additionally, he noted that even if there had been some misconduct on part of prosecution during plea bargaining phase - which wasn't proven beyond reasonable doubt - it would be more appropriate for state courts to handle these issues rather than federal judiciary intervening in every instance where prosecutorial promise might have been broken.