PIERRE - A man who pleaded guilty to rape must be resentenced because a judge gave him a sentence that did not comply with a plea agreement the judge had accepted, the South Dakota Supreme Court ruled.

The high court's unanimous ruling means Ronald Reaves must be resentenced for a conviction of second-degree rape in Pennington County.

Circuit Judge Merton B. Tice Jr. had sentenced Reaves to 20 years in prison with 10 years to be suspended, but the Supreme Court said Tice had already accepted a plea agreement in which prosecutors agreed to limit the sentence to 15 years.

Because a sentence includes both time served behind bars and the time suspended, Reaves got a sentence of 20 years, which exceeded the 15-year cap set in the plea bargain, the high court said.

Reaves was arrested in August 2006 and charged with rape and kidnapping for a rape that occurred in a Rapid City motel, according to court records. The prosecution then reached an agreement with Reaves that capped his prison sentence at 15 years if he pleaded guilty to second-degree rape. The kidnapping charges were dropped as part of the deal.

Reaves pleaded guilty to second-degree rape in April 2007, and Tice told Reaves he would get a chance to withdraw his guilty plea if the judge decided the sentence should exceed the 15-year cap included in the plea agreement.

At a sentencing hearing in June 2007, Tice sentenced Reaves to 20 years in prison, with 10 years suspended. Reaves was not given a chance to withdraw his plea after the judge sentenced him.

Tice later ruled that the prison sentence complied with the plea agreement because Reaves would spend five fewer years in prison than would be allowed in the 15-year cap.

However, the Supreme Court said the sentence was not within the 15-year cap.

The high court said its rulings in prior cases have established that suspended time counts as part of prison sentence, and Reaves might have been required to serve the full 20 years if he did not meet some terms imposed as part of the sentence.

The Supreme Court said trial judges are generally not bound to follow the terms of plea agreements reached by prosecutors and defendants. But Tice had implicitly accepted the plea deal for Reaves, and a trial judge who accepts an agreement is bound to honor it, the justices said.

"A court cannot say it is going to do one thing and then do something else," Justice Richard W. Sabers wrote for the high court.