Dr Frank Olson, a biological warfare scientist, was covertly dosed with LSD at a meeting and died nine days later after falling out of his hotel room in New York City, which was declared a suicide - although some people believe he was murdered.

Now, a newly declassified account from Dr Olson's boss and former head of the Special Operations Division of the Army Chemical Corps has provided a firsthand account of the final moments of the scientist's life.

Vincent Ruwet wrote that following a meeting on November 19, 1953, when the scientist was drugged, Dr Olson appeared agitated compared to his usual social, 'life of the party' behavior.

In the days that followed, Dr Olson became paranoid, barely ate and even disappeared into the night to toss out his wallet, identification badge and money cause he be believed Ruwet asked him to. 

'After about an hour of discussion it became apparent to me that Dr Olson needed psychiatric attention,' Ruwet wrote.

Dr Olson was set to fly out to a mental facility on November 27, telling Ruwet he would see him in the morning to catch the plane.

'At approximately 2:45am Sat. Nov. 28th, 1953, I received a call with from Dr [Sidney] Gottlieb with a message that Dr. Olson had died,' Ruwet's statement concluded.

Dr Olson's body was found outside the Statler Hotel where he was staying on the 13th floor. 

His family was not allowed to see his body, instead being told he had suffered significant facial injuries in the fall and that he had killed himself by jumping. 

However, it was confirmed that he did have LSD in his system at the time of death. 

In 1994, still uneasy with the narrative he'd been given, Dr Olson's oldest son had his father's body exhumed. 

The pathologist ruled that Dr Olson did not suffer disfiguring facial injuries, as the family had been told, and that he had an injury on his head which was consistent with him being murdered in his room and then thrown from the window. 

The CIA's MkUltra program, conducted from 1953 to 1964, aimed at developing procedures and drugs that could be used during interrogations, weakening individuals and forcing confessions through brainwashing and psychological torture.