The police say Mr. Dahmer killed four more times after the brush with the officers. News of the encounter with the Laotian boy led to protests by people who said the police had missed a chance to stop Mr. Dahmer. Others accused the officers of racism and homophobia.

Mr. Dahmer was arrested after a man in handcuffs fled his apartment and alerted police. Officers later found parts of 11 men in the apartment.

Mr. Dahmer told the police he had lured the men to his apartment with the promise of sex, and then killed them. He is charged with 15 killings and has confessed to killing two other men since 1978.

Officer Gabrish, 28 years old, a patrolman for seven years, said he and the other officers believed there was a caring relationship between Mr. Dahmer and the Laotian boy and saw no reason to intervene.

"We're trained to be observant and spot things," he said. "There was just nothing that stood out, or we would have seen it. I've been doing this for a while, and usually if something stands out, you'll spot it. There just wasn't anything there."