The investigation into the assassination of Bulgarian dissident Georgi Markov, murdered with a poison-filled pellet shot into his leg (possibly with a converted umbrella gun") at a bus stop in Britain in 1978, was the most unusual and significant case that medical doctor and forensic specialist Christopher C. Green participated in during his twenty year career as an investigative officer with the Central Intelligence Agency. The reason it was so unique, he says, is that "we had pretty much all of the story from a forensic point of view. We had the body, the thing in the body that he was hit with -- the pellet -- and the stuff from the pellet. We knew that the material used to kill him, ricin, had been under development by a foreign service linked to the incident. We also knew that he had been a target of assassination attempts in the past. The story of him being a target was very well known. So we had information on the means, motive, and the opportunity." In the Markov case, "we had 80 percent of the story," says Green, who is now a professor of diagnostic radiology and psychiatry and behavioral neurosciences at Wayne State University's Detroit Medical Center, where he uses brain imaging techniques to watch how the brain functions as people make decisions. His current work, he says, is a logical outgrowth of his service at the CIA -- where he still serves as a consultant. At the CIA, Green studied how the brain responds to chemicals and neurological agents.