The Boston Strangler adopts the split-screen technique then in vogue (see also The Thomas Crown Affair) to relate the true story of self-confessed mass murderer Albert DeSalvo. Adapted by Edward Anhalt from the book by Gerold Frank, the film covers the years 1962 to 1964, during which time a dozen women were raped and murdered in the Boston area. State-appointed officer John Bottomly (Henry Fonda) arrests as many known sex offenders as he can get his hands on in hopes of finding a clue as to the Boston Strangler's identity. As these things often happen, the police come across the necessary evidence through pure luck. Well-played by Tony Curtis (whose makeup is startling), DeSalvo himself does not appear until an hour into the film. When caught, the schizophrenic DeSalvo insists that he knows nothing of the murders. Under interrogation and hypnosis, his homicidal impulses are exposed. Meticulously cast, The Boston Strangler offers excellent vignettes by Sally Kellerman as the Strangler's only surviving victim and by Hurd Hatfield as an erudite sex pervert. When Boston Strangler was first shown on TV in 1974, a voice-over coda was added, noting that Albert DeSalvo was stabbed to death in prison on November 26, 1973, and that many experts were convinced that he was not the killer but that his confessions were the product of a delusional mind.
~ Hal Erickson, All Movie Guide