Washington ( CNN ) -- A deeply divided Supreme Court ruled Wednesday that criminal defendants who receive inadequate legal advice on pretrial plea bargains can have their sentences overturned , equating that with an unconstitutional and ineffective assistance of counsel . The separate 5-4 decisions in a pair of cases from Michigan and Missouri will have a huge , immediate impact on the 97 % of federal convictions and 94 % of state convictions that stem from guilty pleas . `` This court now holds that , as a general rule , defense counsel has the duty to communicate formal offers from the prosecution to accept a plea on terms and conditions that may be favorable to the accused , '' said Justice Anthony Kennedy , joining four of his more liberal colleagues . `` When the defense counsel allowed the offer to expire without advising the defendant or allowing him to consider it , defense counsel did not render the effective assistance the Constitution requires . '' In a rare oral dissent delivered from the bench , Justice Antonin Scalia called the majority decision `` absurd '' and `` unheard-of . '' In unusual detail , the opinion lays out specific guidelines to defense counsel , saying they must relay plea bargain offers from the prosecution , regardless whether the lawyer believes them to be proper . The case from Michigan involved Blaine Lafler , convicted of assault with intent to murder and other charges , after shooting and seriously wounding a woman . The state twice offered to dismiss two of the charges , and recommended a reduced sentence in return for a guilty plea . Lafler claims he rejected the offers after his lawyer convinced him the prosecution could not prove the most serious charge . The defendant was convicted and received 185 to 360 months behind bars . In Missouri , Galin Frye was charged with driving on a revoked license . Three previous convictions on the same charge meant he could be sentenced to up to four years in prison . Court records shows he was not told about two pretrial plea bargain offers that would have reduced his jail time . A week before his preliminary court hearing , the man was again arrested on the same offense . With no deal on the table , he subsequently pleaded guilty and received three years imprisonment . `` There appears to be a reasonable probability Frye would have accepted the prosecutor 's original offer of a plea bargain if the offer had been communicated to him , '' Kennedy said in his ruling , `` because he pleaded guilty ( later ) to a more serious charge , with no promise of a sentencing recommendation from the prosecution . '' Justices Ruth Bader Ginsburg , Stephen Breyer , Sonia Sotomayor and Elena Kagan supported Kennedy , who again proved to be the `` swing '' vote for the majority . Both cases were sent back to lower courts to sort out the new sentencing guidelines . In his dissent , Scalia warned criminal defendants will now flood courts with new claims of bad legal representation . `` The court today embraces the sporting chance theory of criminal law , in which the state functions like a conscientious casino operator , giving each player a fair chance to beat the house , that is , serve less time than the law says he deserves , '' he said . `` And when a player is excluded from the tables , his constitutional rights have been violated . '' He added , `` In today 's cases , the court 's zeal to bring perfection to everything requires the reversal of perfectly valid , eminently just convictions , '' Scalia said . `` It is not wise ; it is not right . '' Chief Justice John Roberts and Justices Clarence Thomas and Samuel Alito joined all or part of the dissent . The cases are Lafler v. Cooper ( 10-209 ) and Missouri v. Frye ( 10-444 ) .
Defense attorneys have a duty to give good advice on plea deals , the court rules . They must do so to provide `` the effective assistance the Constitution requires '' In dissent , Justice Scalia calls the decision `` absurd '' and `` unheard-of ''