Police and prosecutors won't say who they have interviewed or intend to interview or how many individuals have been questioned. But one police officer indicated that questioning people again in investigations that span years can be helpful, especially if circumstances have changed.

"Relationships change, and over time someone may not feel that loyalty or fear that they did at the time and now may be willing or able to say something they wanted to say or could've said at the time but weren't comfortable saying," said Big Island police Lt. Randall Medeiros, speaking in general terms.

The stepped-up investigation comes amid a resurgence in publicity on Peter Boy's case.

The release last month of 2,000 pages of previously confidential documents resulted in a flurry of news stories, prompting renewed calls for action in the case. Among the revelations in the documents: Peter Boy's sister, then 5, told a psychologist that she had seen her brother's dead body in 1998 on two occasions. A team of child-welfare advocates also said in 1998 that they believed Peter Boy's parents may have been responsible for his disappearance, according to the state Department of Human Services documents.

The parents have denied harming their son.

Peter Boy, who suffered from repeated physical abuse, disappeared in the spring or summer of 1997 under suspicious circumstances. Police initially investigated his disappearance as a missing person's case but later classified it as a homicide investigation, turning over a final report to prosecutors in 2000. No one has been charged, nor has a suspect been named.

Jay Kimura, prosecuting attorney for Hawai'i County, said progress was being made in the case. He would not be more specific.

Kimura indicated that his office would pursue prosecution only if prosecutors believe they have enough evidence to prove a case beyond a reasonable doubt.

"As with any case, if there is sufficient admissible evidence, we will go forward with this case," Kimura said.

Based on what has been publicly reported, defense attorneys, former prosecutors and others said they believe Kimura's office has enough circumstantial evidence to obtain a grand jury indictment but not enough to prove a homicide charge at trial. To get an indictment, prosecutors would have to show a reasonable probability that a crime occurred. To obtain a guilty verdict at trial, prosecutors must prove the case beyond a reasonable doubt, a higher legal threshold.

Because people cannot be tried twice for the same crime and because authorities are under no deadline for filing murder charges, some attorneys said prosecutors are wise to bring the case to court only when they have the strongest evidence possible.

The biggest problems in the Kema case are lack of a body and uncertainty of whom to charge, attorneys said.

Without a body, prosecutors would have difficulty proving Peter Boy is dead, much less the cause and manner of death and whether someone intended to or knowingly caused his death, the attorneys said.

Deciding whom to charge could be equally problematic, they said.

If prosecutors sought charges against one or both of Peter Boy's parents, the parents would only have to point the finger at each other and that could be enough to create reasonable doubt, according to Earle Partington, a criminal defense lawyer and former Ho-nolulu prosecutor.

"It's a serious problem," Partington said.

One way to address such a shortcoming, the attorneys said, would be to try to work an immunity deal with the spouse believed to be least culpable.

Peter Boy's parents, Peter Kema Sr. and Jaylin Kema, separated earlier this year and Jaylin Kema, 35, has a restraining order against her husband through January 2008. In court papers, she said her husband had been abusive.

The couple's separation has generated speculation that authorities may try to reach an immunity deal with Jaylin Kema in exchange for her testimony.

Her attorney, Harry Eliason, would neither confirm nor deny that he has been approached about such a deal, citing attorney-client privilege.

Eliason said his client has not been questioned by authorities since at least 2003, when he began representing her. He previously said the evidence points to Peter Boy's father and not his mother.

Peter Kema Sr. is believed to be on the Big Island, but could not be reached for comment for this story.

Kimura, the Big Island prosecutor, said his office eventually plans to ask the state attorney general's office for help in the Peter Boy case once police, prosecutors and the attorney general's office decide the best way for the state to provide that help.

The attorney general's cold case unit, established to help solve old cases, offered its investigative expertise late last year, but the parties still are in discussions about what form that may take, Kimura said.