DALLAS -- A doctor who worked at the hospital where President John F. Kennedy and Lee Harvey Oswald were treated says Kennedy's fatal head wound "had to have come from the front."

Dr. Charles Crenshaw is breaking his 29-year silence on the pTC subject by talking to two national television shows, ABC's "20/20" and the syndicated "Now It Can Be Told." He has written a book, "JFK: Conspiracy of Silence," to be published next week.

In his interviews, Dr. Crenshaw says the shot to the head could not have been fired by Oswald.

He also tells of receiving a phone call from President Lyndon Johnson, who demanded a "deathbed statement" from Oswald after he was shot by Jack Ruby. Oswald made no known dying statements.