Dr. Stuart Grassian, a psychiatrist at Harvard Medical School who studies the effects of solitary confinement, said the conditions went too far. ''I could imagine a sober society living with capital punishment,'' he said, ''but I can't imagine a civilized society living with the punishment of driving a prisoner insane.''

The sentence's harshness, though not its originality, startles those who know the judge. Judge Martin, 62, a former United States Attorney and a defense lawyer, is seen as a fair sentencer -- thoughtful and independent-minded but intransigent. The judge, who refused to comment about the Felipe case, has on occasion repeated with evident pride a colleague's appraisal: ''You must be doing something right. You're getting reversed almost as much as Jack Weinstein'' -- the famously independent Federal judge who sits in Brooklyn.

That Mr. Felipe, a man of charisma and intelligence, is nonetheless a ruthless criminal is not in dispute. His accounts of his background vary. He has said that his mother was a prostitute and that both parents are now dead. At the age of 9, he was sent to prison for robbery. On his 19th birthday in 1980, he arrived in the United States during the Mariel boatlift. In short order, Mr. Felipe became a street thug, settling in Chicago. There he joined the Latin Kings, a Hispanic organization established in the 1940's.

He moved to the Bronx. One night in 1981, in what has been described as a drunken accident, he shot and killed his girlfriend. He fled to Chicago and was not apprehended until 1984. Sentenced to nine years for second-degree manslaughter, he ended up at Collins Correctional Facility in Helmuth, N.Y.

At Collins, he found an inmate system lorded over by black gangs and white guards. In 1986, he started a fledgling New York prison chapter of the Latin Kings. In a manifesto that followers circulated, he laid out elaborate laws and rituals, emphasizing Latin pride, family values, rigorous discipline and swift punishment.

He was paroled in 1989 but by 1991 had returned to prison. He was eventually sent to Attica for a three-year sentence for possession of stolen property. His word spread, not least because he wrote thousands of letters, his prose a mix of flamboyant grandiosity and street bluntness. As King Blood, Inka, First Supreme Crown, Mr. Felipe corresponded with Latin Kings in and out of prison. (At its peak, the gang was estimated to have about 2,000 members.) He soared with self-aggrandizement, styling himself as both autocratic patriarch and jailhouse Ann Landers, dispensing advice about romance, family squabbles, schoolyard disputes.

But in 1993 and 1994, disciplinary troubles erupted throughout the Latin Kings, with members vying for power, filching gang money, looking sideways at the wrong women. Infuriated, King Blood wrote to his street lieutenants: B.O.S. (beat on sight) and T.O.S. (terminate on sight).