Dr. Peter D. King, 73, psychiatrist who specialized in treating young people and did extensive research on schizophrenia and autism. King, who had his own family practice for more than three decades, served as a psychiatrist at Los Angeles County's Juvenile Hall and taught at UCLA and, for most of his career, at USC. Using his research at County-USC Medical Center and elsewhere, King wrote more than 50 books and papers on his work in autism and schizophrenia, on hospital administration and on other subjects, including the effects of alcohol and tranquilizers on human coordination and judgment. In 1982, King protested publicly when the Reiss-Davis Child Study Center, where he had done research on autism, acknowledged destroying its early research records. King told The Times that, while patients' confidentiality must remain sacrosanct, research records should be preserved "as a responsibility to humankind and the scientific community." Educated at the University of Chicago, King served in the Army Air Corps and later held psychiatry positions at facilities in Altoona, Pa., and Madison, Ind., before moving to Los Angeles in 1959. Off duty, King wrote poetry and was a champion runner, earning a gold medal in the 1983 Los Angeles Triathlon. On Monday in Los Angeles of liver cancer.