Central Intelligence Agency employees murdered military scientist Frank Olson in 1953 after he raised concerns about testing chemical and biological weapons on human subjects without their consent, according to a lawsuit brought by his two sons. Eric and Nils Olson, in a complaint filed against the U.S. yesterday in Washington, said the agency has covered up the cause of their father's death for 59 years. Frank Olson, who the CIA admitted was given LSD a few days before his death, didn't jump from a 13th floor window of the Statler Hotel in New York City, but rather was pushed, they claim. The circumstances surrounding the death mirrored those detailed in an assassination manual that, upon information and belief, the CIA had drafted that same year," Scott Gilbert, a lawyer for the Olsons, wrote in the complaint. Olson's family has tried to piece together how Frank Olson died and the circumstances surrounding his death ever since a 1975 government report on CIA activities in the U.S. said that he committed suicide after being given LSD without his knowledge. Preston Golson, a CIA spokesman, said ... that the agency's covert behavioral research program known as MK-ULTRA was investigated in 1975 by the Rockefeller Commission and the Church Committee, and in 1977 by the Senate Select Committee on Intelligence and the Senate Subcommittee on Health and Scientific Research. Olson's sons said in the suit they have asked repeatedly "to be told the truth" about their father's death. "Each time, the government has responded with falsehoods," they said.