NEW YORK — George Whitmore Jr., an eighth-grade dropout who confessed in 1964 to three New York murders he did not commit, and whose case became instrumental in establishing historic legal reforms — including the Supreme Court's 1966 ''Miranda'' ruling, which protects criminal suspects — died Oct. 8 in a Wildwood, N.J., nursing home. He was 68.
The cause was a heart attack, his daughter Regina said.
Mr. Whitmore was 19 in April 1964 when he was picked up on a Brooklyn street for questioning about an attempted rape in the neighborhood the night before. A soft-spoken young man, he had tried hard in school but dropped out at 17, moved to Brooklyn, and was waiting for a ride to work when the police pulled over and started asking him questions.
He later said he had secretly been pleased at being asked for help in solving a crime.
But when his interrogation ended several days later, Mr. Whitmore had confessed to the attempted rape and to the rape and killing a few weeks earlier of another woman in the neighborhood, Minnie Edmonds. He had also confessed to the double slaying in Manhattan on Aug. 28, 1963, of two women.
Called ''the Career Girl Murders'' in newspaper headlines, the killings of Janice Wylie, 21, a Newsweek magazine researcher, and Emily Hoffert, 23, a teacher, had been the focus of an eight-month investigation.
Mr. Whitmore recanted his confession and he consistently said afterward that the police had beaten him and that he had signed the confession without knowing what it was. In the case of the Wylie-Hoffert slayings, he said, he could provide the names of a dozen people who saw him on that day and who would remember it, because it was the day of the civil rights march on Washington, when Martin Luther King Jr. gave his ''I Have a Dream'' speech. He and everybody else in Wildwood had watched it on television and talked about it.
In 1964, Mr. Whitmore was convicted by a Brooklyn jury on the charges of attempted rape. Though the verdict was overturned because jurors were found to have been reading newspaper accounts of the case, which referred to Mr. Whitmore as the ''prime suspect'' in the Career Girl Murders, he was tried a second time. He was convicted again, but the verdict was again thrown out.
By 1965, Manhattan prosecutors had evidence that Mr. Whitmore was wrongly accused. They had linked the slayings to Richard Robles, a recently released prisoner who would be convicted of the crime and who remains in prison.
Defense lawyers argued that Mr. Whitmore's confession to the Edmonds slaying, elicited in the same interrogation, had therefore been coerced, too.
Selwyn Raab, a reporter, found a dozen witnesses who saw Mr. Whitmore in Wildwood on the day of the double murder. They had bumped into him in the homes of friends and relatives watching King's speech, Raab wrote in The New York World-Telegram.
''Whitmore's case showed how fragile the whole system was, and still is,'' Raab said in an interview Sunday. ''Even now, police use the same techniques to manipulate suspects into giving false confessions. And 90 percent of convictions are still based on confessions.''
The Supreme Court cited Mr. Whitmore's case as ''the most conspicuous example'' of police coercion in the country when it issued its 1966 ruling establishing a set of protections for suspects, including the right to remain silent, in Miranda v. Arizona.