One of today's most controversial areas of criminal law - the insanity defense - may never quite recover any degree of acceptability after the rough going-over it gets in an amazing two-part ''Frontline'' documentary.
The Mind of a Murderer (PBS, Part 1, Monday, March 19, 8-9; Part 2, Monday, March 26, 8-9; check local listings for repeats) traces the arrest, questioning, and trial of the ''Hillside Strangler,'' who raped, tortured, and murdered 13 young women in a crime wave that terrorized Los Angeles for five months in 1977. He was finally caught in Bellingham, Wash., after killing two young women there.
Using a court order, BBC-''Frontline'' producer Michael Barnes obtained the right to copy more than 65 hours of taped interviews between Ken Bianchi and the psychiatrists, recorded in jail shortly after his arrest. Most of these experts found Bianchi to be the victim of a rare mental disorder in which multiple personalities inhabit the same body, a la ''The Three Faces of Eve'' and ''Sybil.''
Without resorting to gruesome photos or titillating material, but still incorporating some disturbing language and unnerving descriptions, the documentary manages to tell a distasteful story with as much taste as possible.
In some astounding footage, the viewer can see the ''bad boy'' personality -Steve - emerge and boast of the killings, and then the ''good boy'' personality -Ken - deny any knowledge of the events. The viewer, like most of the experts, may find the incredible jailhouse testimony basically believable.
But it was not until a prosecution-appointed psychiatric expert delved deeper into the charade, tested the testimony, investigated past facts, questioned the motivation, and uncovered great discrepancies in the phony multiple-personality stance that Ken Bianchi was finally forced to abandon his plea of insanity and plead guilty so as to avoid the death penalty.
According to writer-director Michael Barnes - who produced this extraordinary documentary under the aegis of executive producer David Fanning of WGBH, Boston, and a consortium of public television stations including KCTS, Seattle, WNET, New York, WPBT, Miami, and WTVS, Detroit - this film ''raises grave issues over the role of psychiatric evidence.'' Grave issues; even graver doubts.
Certainly, nobody who views ''The Mind of a Murderer'' will ever be able to forget the charges and countercharges of ''incredible naivete'' by the judge and psychiatrists. If such experts cannot be believed, how can the insanity defense ever be judged by a jury?
''Frontline'' is now the only regularly scheduled documentary series on American television (magazine shows excluded). It has been producing shows that are consistently interesting, if sometimes uneven. With ''The Mind of a Murderer'' - an indelibly startling piece of prizewinning work - it steps right into the forefront of electronic journalism.