According to director Burt Topper, Victor Buono puffed smoke into his eyes to create tears for a particular scene.
Released nearly three months after the real Boston Strangler claimed his final victim.
The director and Victor Buono had a strained working relationship during the production. In addition to Buono having some trouble hitting his marks properly, he objected to some of the scenes that he felt were too suggestive. For the scene when he attacked Diane Sayer, it was supposed to be implied that she was nude (even though actual nudity could not be depicted onscreen at this time because of the Hays Code). Buono actually walked off the set for an entire day in protest. The scene was eventually shot with Davison having apparently just stepped out of the shower, but being almost entirely hidden by the pebbled glass shower door as well as Buono's much larger frame.
Victor Buono was the best-known actor in the film, despite having only recently begun his film career. However, he signed for the film just after having gained an Oscar ® nomination for his famous, fame-making role in What Ever Happened to Baby Jane? (1962) and consequently had quite considerable power over the film, which he exercised. The script was much altered to overcome his various objections to it.
The unforgiving, domineering mother, who serves as the "motive" for Victor Buono's killing spree, is "cast against type." She's portrayed by Ellen Corby, who usually played kindly school teachers or friendly housekeepers, and later came to fame as the beloved, gently non-judgmental Grandma on the TV hit The Waltons (1972).