Somewhere in the world today, the killer of Sweden's prime minister has gone a third of the way to the perfect crime.

The 25-year statute of limitations on the murder of Olof Palme will expire Feb. 28, 2011. If the killer is identified after that, there can be no legal punishment. The rout of Sweden's hapless investigation will be complete.Since Palme was shot walking home from a movie nearly nine years ago, a petty criminal has been convicted and released for lack of evidence. Investigators have been sacked, books written and 15,000 tips scrutinized - so far in vain.

Christer Pettersson was convicted of Palme's murder in 1989, largely on the basis of Lisbeth Palme's testimony that she saw him on the scene shortly after her husband's murder. A higher court overturned the verdict, ruling there was insufficient evidence. Pettersson served a year in prison, then was freed and paid compensation in 1990. He's now 47 and lives in Sweden.

Conspiracy theories have pinned the killing on nearly everybody from Kurdish rebels to Sweden's own secret police. The suggested motives have been revenge, politics or just street crime.

Most theories are plausible because Palme was so controversial.

A powerful and charismatic leader, Palme in the early 1980s had tried to mediate in the Iran-Iraq war and also had been accused of supporting arms sales to India by Swedish companies.

In the 1970s, Palme, a Social Democrat, compared the U.S. bombing of Cambodia to a Nazi blitzkrieg and once walked arm-in-arm with North Vietnam's ambassador in a parade.

Today, with 25 detectives still at work on the mystery surrounding his death, the government is planning an investigation of the investigation - a decision that could bring still more embarrassment to Swedish law enforcement.

Sweden's Justice Ministry last month named a commission to review nine years of work, hoping to find out what went wrong.

"Many people mistrust the investigation," says Claes Kring, a Justice Ministry official.

"The only thing that can straighten all this out is to let some people - whom citizens have confidence in - go through the material and make their own opinion."

The commission won't finish its work until mid-1996. Even so, deputy prosecutor Solveig Riberdahl doubts anybody will be found before the crime's statute of limitations expires.

"The only thing that could change this would be finding proof that the perpetrator is dead, and that's not likely," Riberdahl said in a newspaper interview.

Although the number of investigators may be reduced next year, police say they won't give up.

But as time passes, more people blame a conspiracy or incompetence for the failure of an investigation that so far has cost $36 million and continues to cost about $1.3 million a year.