SIDNEY GOTTLIEB was living vindication for conspiracy theorists that there is nothing, however evil, pointless or even lunatic, that unaccountable intelligence agencies will not get up to in the pursuit of their secret wars.

For two decades he ran a CIA programme aimed at nothing less than control of the human mind. Its tools were mind-altering drugs, most notably LSD. Its subjects, almost all of them unwitting, were society's outcasts: prostitutes and their clients, mental patients, convicted criminals - people, in the words of one of Gottlieb's colleagues, "who could not fight back". At the end of it all, just as the conspiracy theorists would have predicted, Gottlieb himself pronounced that the entire exercise had been a waste of time.

The project, called MKUltra, began in 1953, two years after Gottlieb had joined the agency as chief of its technical services division. It was a period when paranoia ruled at Langley, the Virginia headquarters of the CIA. At home, McCarthyism was at its apogee. Abroad, the Soviet Union and increasingly China were regarded as mortal threats. America had lost its nuclear monopoly, while field operations against Moscow would soon be thrown into turmoil by the obsession of James Jesus Angleton, head of CIA counter-intelligence, that the agency had been penetrated by a mole at the highest levels.

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Its leadership was also fixated by the fear that the great Communist powers were perfecting techniques of mind control - The Manchurian Candidate made real. The CIA, therefore, had to get its blow in first. Enter Sidney Gottlieb.

He was born in 1918 the son of Hungarian Jewish immigrants, but never adopted the faith; indeed much of the rest of his life was a search for religious fulfilment, via agnosticism, Christianity and even Zen Buddhism. His scientific abilities however were evident when he graduated summa cum laude in chemistry from the University of Wisconsin in 1940.

To his enduring disappointment, a club foot barred him from active service in the Second World War . Instead his patriotism would find its outlet in the CIA, where the war had never ended. Only the enemy had changed.

Gottlieb's contribution was to oversee MKUltra. From the early 1950s through most of the 1960s hundreds of American citizens were administered mind-altering drugs. One mental patient in Kentucky was given LSD for 174 consecutive days. In all the agency conducted 149 mind-control experiments. At least one "participant" died as a result of the experiments and several others went mad.

The most bizarre brainwave of Gottlieb (himself a frequent user of LSD) was to set up a string of CIA-controlled brothels in San Francisco which operated for eight years. Prostitutes would slip drugs to their customers, and the results would be observed by agency officials through two-way mirrors. Such was the clandestine contribution of the city of flower power to the national war effort in Vietnam. Unfortunately its visible contribution, of spawning a hippy movement which led the protest against the war, was far more effective.

Gottlieb's inventiveness also ran to a variety of assassination plots against various foreign targets. He perfected a contaminated handkerchief for use against an Iraqi colonel, poisoned presents that were to eliminate the troublesome Fidel Castro, and a poisoned dart designed to get rid of Patrice Lumumba, Communist sympathiser and leader of the Congo. Needless to say, none of the devices worked.

Gottlieb retired in 1972, having concluded that all his work had been useless. That however did not deter the CIA from awarding him its highest honour, the Distinguished Intelligence Medal, before it destroyed the bulk of the MKUltra files.

In his way Sidney Gottlieb was a loyal servant of American government - but his ways differed only in degree from the experiments for which the wartime allies, among them the US, sent Nazi doctors to the gallows for crimes against humanity. But, as John Marks, author of The Search for the Manchurian Candidate: the CIA and mind control (1979), the definitive work on the subject, wrote: "He never did what he did for inhumane reasons. He thought he was doing exactly what was needed. And in the context of the time, who could argue?"

Gottlieb's life after the CIA resembled a quest for atonement. With his wife Margaret, he spent 18 months in India running a leper hospital. He then moved back to rural Virginia, where he indulged two longstanding hobbies, folk dancing and goat herding. He devoted his final years to work in a hospice, looking after the dying.

Sidney Gottlieb, chemist and intelligence officer: born New York 3 August 1918; married 1942 Margaret Moore (two sons, two daughters); died Washington, Virginia 7 March 1999.