Hundreds of inmates may have served more time behind bars than they needed because of conflicting state policies and practices on when prison sentences are to run concurrently or consecutively.

The state Legislature is considering two bills, House Bill 141 and Senate Bill 106, that would change a Hawaii sentencing law for the second time in three years in an attempt to clarify for the Department of Public Safety how sentences are to be calculated when judges do not specify whether an inmate facing more than one prison term should serve the time back-to-back.

Starting in 2005, as their release dates approached, hundreds of inmates were told by DPS they would have to serve additional time — sometimes years more — because their sentences were previously miscalculated. DPS said it was complying with a 1986 law that had been ignored prior to that, which mandated consecutive sentencing unless judges specified otherwise.

While the state did not keep count of how many were kept behind bars for longer periods, it could be in the hundreds. Two inmates whose prison terms were extended because of the recalculations filed a federal class-action lawsuit in 2007 and more later joined the suit.

“Simply put, this bill could save the state of Hawaii millions of dollars annually without compromising public safety,” the American Civil Liberties Union, Hawaii chapter, said in written testimony on one of the bills. “These extended sentences appear to have been inconsistent with the sentencing judges’ intentions and did not reflect the inmates’ danger to society; worse still, many of these recalculations were incorrect, and the state is now battling a class-action lawsuit seeking damages for these over-detentions.”

Opponents say the proposals presume to know what the judges intended when they handed down prison sentences and legislates changes to the sentences in violation of the constitutional separation of powers doctrine.

At the heart of the issue is whether judges intended inmates to serve their prison terms consecutively when they sentenced them.

The 1986 law specified that when a defendant already serving a sentence in one criminal matter gets sentenced in a subsequent case, the sentences shall run consecutively, or back-to-back, unless the judge ordered them to run concurrently.

It was the practice of DPS before 2005, however, to calculate what is referred to as an inmate’s “max-out date” based on the assumption that sentences would typically run concurrently. A max-out date assumes the longest amount of time an inmate will have to remain in prison without parole.

Before 2005, state Public Defender Jack Tonaki said, running sentences concurrently was the practice and understanding of not just the DPS, but defense lawyers, prosecutors and state judges.

“Unequivocally,” Tonaki said.

Consecutive sentences are outside normal practice, Tonaki said. So when a judge imposes them, there would have been extensive argument and the judge would have stated the reasons for imposing the harsher penalty, he said.

Because of the confusion, the Legislature in 2008 changed the law to mandate concurrent sentencing. But because the change occurred in 2008, DPS continues to apply the old law to inmates sentenced before the change.

The bills under consideration this year would make the 2008 change retroactive to 1986. Supporters say it will end the unequal treatment of potentially thousands of inmates and save the state money in court, legal and prison costs.

Robert Naehu Jr. was expecting to get out of prison, according to his original max-out date, on May 7 last year. However, on Oct. 15, 2009, he received a letter from DPS informing him that there were “discrepancies” in the computation of his maximum term release date and that the new date is June 12, 2013.

By the time Naehu sent a letter to attorney Jack Schweigert asking for his help three months ago, he said he had been going to therapy “because I can’t sleep and I’m very stressed out” over the change in his release date.

Schweigert went to court to seek amendments to the sentences Naehu received in 1990, 1994 and 2005 to add a phrase that they are to run concurrently with all other sentences. The judge who imposed the 2005 sentence, and who is still on the bench, agreed to amend his sentence. Another judge amended the 1990 and 1994 sentences because the judges who imposed them are either dead or no longer on the bench.

In all three cases, the prosecutor did not oppose the amendments. DPS released Naehu in February.

Other inmates have also been getting their sentences amended.

Tonaki said he can’t recall a single case in the dozens his office has handled in which the prosecutor opposed amending a judgment.

Honolulu City Prosecutor Keith Kaneshiro said he only recently became aware that his prosecutors were not opposing amending judgments, a practice that was carried over from the previous administration. He said from now on his department will follow the law, which means requests for amended sentences will not go unopposed.

But not all inmates whose max-out dates DPS recalculated and extended contacted lawyers to have their sentences amended, said state Sen. Maile Shima­bu­kuro, who introduced SB 106.

“It’s an issue of fairness,” she said.

State Rep. Faye Hanohano said she introduced HB 141 because of the expense to the public defender, who winds up with many of the inmates’ requests for amended sentences, for researching the cases, filing the necessary paperwork and going to court. She said there is the added expense for housing inmates longer than perhaps judges intended.

“It’s costing us money,” she said.

The offices of the state attorney general and the Ho­nolulu prosecutor oppose the retroactive application of the 2008 change because they said judges were presumed to have known the law when they handed down sentences.

The DPS said retroactive application will require the department to review the max-out dates of all of the approximately 6,000 inmates now in custody and 1,800 on parole. The department said it would also expose the state to lawsuits from inmates kept in custody past their original max-out dates.