Fred West (Dominic West, right, with Emily Watson) murdered at least 11 women.

“The Wire’s” Dominic West takes a chilling turn as real-life British serial killer Fred West in the Sundance Channel film “Appropriate Adult” (Sat., 10 p.m.). Yet, throughout the entire 2½-hour drama, viewers never see Fred commit a single crime.

“I think it would have been wrong to have shown anything other than reported action,” West says. “Then it would have been horror or pornography.”

Fred was responsible — along with his wife, Rose — for the murder of at least 11 young women between 1967 and 1987. The film focuses on Fred’s arrest in 1994 and the investigation that led to his admitting to a portion of the murders.

“Appropriate adult” is a British legal term that applies to Janet Leach (Emily Watson), the court-appointed citizen advocate tasked with explaining the charges to the mentally unstable Fred.

“He didn’t have the normal sort of value systems that we have,” West says. “There was no difference to him between killing the family pig, which he did when he was 13, and killing an unwanted girlfriend. It is a childlike, monstrous ego that he had, that had none of the checks that most adults have.”

Much of the film plays out in interrogation rooms, as Fred manipulates Janet and the police. West and the film’s writers had access to more than 100 hours of police interviews, some of which made it into the film verbatim. “It was never difficult to put across the nature of his evil and of his malignancy just because the words are so powerful and so appalling,” West says. “You could see what kind of a psychopath he was.”