DENVER (AP) _ Doctors tried for five years to fuse the 10 personalities of Ross Carlson so he could stand trial for the murder of his parents. His attorney believes death succeeded where the doctors failed.

''I think death was the final solution that caused the fusion of the personalities, which the state hospital refused to do,'' said Walter Gerash, who represented Carlson throughout the case.

Carlson died Thursday at University Hospital of complications from leukemia. He was 19 when the crimes were committed, and 25 when he died.

He was charged with the Aug. 18, 1983, killings of his parents, Rod and Marilyn Carlson, whose bodies were found beside an isolated road in Douglas County, just south of Denver. They were found face down, shot to death.

He was arrested and charged with the deaths. He pleaded innocent by reason of insanity and a psychiatrist said he thought the teen-ager was suffering from multiple-personality disorder.

Therapists eventually said they identified as many as 10 personalities and Carlson spent five years in the Colorado State Hospital in Pueblo.

But Gerash said, ''They hired debunkers instead people who know how to treat the disorder.''

Gerash said he had hoped therapy would ''fuse'' Carlson's personalities, making him well enough to stand trial.

Carolyn Herzberger, a spokesman for Colorado State Hospital, refused to comment Friday on the case. ''Anything we did in an attempt to fuse his personalities is privileged information about a patient, and no hospital in the country is going to discuss that,'' she said.

Only last month, Douglas County Senior Judge Robert Kingsley ruled that Carlson was competent to stand trial, and one was scheduled next month.

Kingsley said he thought Carlson's personalities were simply a good acting job.

Just days after the competency ruling, Carlson was rushed to the hospital after a vomiting spell. On Nov. 7, doctors confirmed a diagnosis of acute lymphoblastic leukemia.

Carlson initially refused chemotherapy because his wrists were shackled. Gerash said some of his personalities felt threatened by the restraints. The shackles were removed and chemotherapy began.

On Sunday, Carlson tried to wrestle a gun from a deputy sheriff guarding him. His attorney said it was an attempt to commit suicide.

On Thursday, he died. The controversy continues.

Gerash said he talked to almost all of the personalities, and said no one really understood Carlson or his illness.

''Most of the time I talked to Justin. He varied a lot between Justin, and another personality Steve, a 40-year-old person who was very articulate. In 1985, he developed another personality, Holden, a hospital personality. I also saw a weeping child, Blue, handling the leukemia. There was a child of 11, Gray, and I saw Black. I was threatened once by Black.

''I saw another guy, Norman, who was prehomicidal, a tough-talking New Yorker who smokes. Carlson was allergic to smoke, but I saw him smoke,'' he said.

However, the judge was not the only one who doubted Carlson's diagnosis. A columnist in the Denver Post on Sunday criticized the $1,180 a day spent on caring for Carlson's leukemia, which also will be billed to taxpayers because his trust fund ran out.

The columnist, Woody Paige, wrote: ''Doctors have talked to a myriad of Carlson-produced personalities - Steve, Justin, Black, Blue, Gray, Stacey, Michael, Norman and the Anti-christ. Where's Dopey and Sneezy? Is this one person, or a touch football team?

''I'm certainly not making light of mental illness. Trust me. It is a serious matter. But the Mighty Carlson Art Players and their act is beginning to wear thin.''

Gerash said he understands the anger from the community.

''When you kill your father and mother, that's a wholesale violation of the Ten Commandments,'' he said.