Claims of ineffective assistance at trial are commonplace even though trials take place under a judge’s watchful eye. Challenges to plea agreements based on misconduct by defense lawyers will presumably be common as well, given how many more convictions follow guilty pleas and the fluid nature of plea negotiations.

Justice Scalia wrote that expanding constitutional protections to that realm “opens a whole new boutique of constitutional jurisprudence,” calling it “plea-bargaining law.”
Scholars agreed about its significance.

“The Supreme Court’s decision in these two cases constitute the single greatest revolution in the criminal justice process since Gideon v. Wainwright provided indigents the right to counsel,” said Wesley M. Oliver, a law professor at Widener University, referring to the landmark 1963 decision.
In the context of trials, the Supreme Court has long established that defendants were entitled to new trials if they could show that incompetent work by their lawyers probably affected the outcome. The Supreme Court has also required lawyers to offer competent advice in urging defendants to give up their right to a trial by accepting a guilty plea. Those cases hinged on the right to a fair trial guaranteed by the Sixth Amendment.

The cases decided Wednesday answered a harder question: What is to be done in cases in which a lawyer’s incompetence caused the client to reject a favorable plea bargain?
Justice Kennedy, joined by Justices Ruth Bader Ginsburg, Stephen G. Breyer, Sonia Sotomayor and Elena Kagan, acknowledged that allowing the possibility of do-overs in cases involving foregone pleas followed by convictions presented all sorts of knotty problems. But he said the realities of American criminal justice required to the court to take action.

Some 97 percent of convictions in federal courts were the result of guilty pleas. In 2006, the last year for which data was available, the corresponding percentage in state courts was 94.
“In today’s criminal justice system,” Justice Kennedy wrote, “the negotiation of a plea bargain, rather than the unfolding of a trial, is almost always the critical point for a defendant.”

Quoting from law review articles, Justice Kennedy wrote that plea bargaining “is not some adjunct to the criminal justice system; it is the criminal justice system.” He added that “longer sentences exist on the books largely for bargaining purposes.”

One of the cases, Missouri v. Frye, No. 10-444, involved Galin E. Frye, who was charged with driving without a license in 2007. A prosecutor offered to let him plead guilty in exchange for a 90-day sentence.

But Mr. Frye’s lawyer at the time, Michael Coles, failed to tell his client of the offer. After it expired, Mr. Frye pleaded guilty without a plea bargain, and a judge sentenced him to three years.

A state appeals court reversed his conviction but said it did not have the power to order the state to reduce the charges against him. That left Mr. Frye roughly where he started, with the options of going to trial or pleading guilty without the benefit of a plea deal.

Justice Kennedy wrote that Mr. Frye should have been allowed to try to prove that he would have accepted the original offer. But that was only the beginning of what Mr. Frye would have to show to get relief. He would also have to demonstrate, Justice Kennedy wrote, that prosecutors would not have later withdrawn the offer had he accepted it, as they were allowed to do under state law. Finally, Justice Kennedy went on, Mr. Frye would have to show that the court would have accepted the agreement.