Editing John Wayne Gacy (section)

===Surveillance===
The Des Plaines police confiscated Gacy's Oldsmobile and other PDM work vehicles. Surveillance teams (consisting of officers Mike Albrecht and David Hachmeister, and Ronald Robinson and Robert Schultz) monitored Gacy as the investigation continued.{{sfn|Cavendish|1990|p=1915}}{{sfn|Sullivan|2000|p=41}} The following day, investigators received a phone call from Michael Rossi, who informed the investigators of Gregory Godzik's disappearance and the fact that another PDM employee, Charles Hattula, had been found drowned in an Illinois river earlier that year.{{sfn|Sullivan|2000|pp=53–55}}{{sfn|Sullivan|2000|pp=123–127}}

On December 15, Des Plaines investigators obtained further details of Gacy's battery charge, learning Jeffrey Rignall had reported that Gacy had lured him into his car, then chloroformed, raped and tortured him before dumping him in Lincoln Park. In an interview with Gacy's former wife the same day, they learned of the disappearance of John Butkovich.{{sfn|Sullivan|2000|pp=84–93}} The same day, the class ring was traced to a John Alan Szyc.{{sfn|Sullivan|2000|pp=53–55}} An interview with Szyc's mother revealed that several items from her son's apartment were also missing, including a Motorola television.{{sfn|Sullivan|2000|pp=99–104}}{{sfn|Nelson|2021|p=243}}

By December 16, Gacy was becoming affable with the surveillance detectives, regularly inviting them to join him for meals in restaurants and occasionally for drinks in bars or at his home. He repeatedly denied involvement with Piest's disappearance and accused the officers of harassing him because of his political connections or his recreational drug use. Knowing these officers were unlikely to arrest him on anything trivial, he taunted them by flouting traffic laws and succeeded in losing his pursuers more than once.{{sfn|Amirante|2011|p=89}} That afternoon, Cram consented to a police interview, in which he revealed that, because of his poor timekeeping, Gacy had once given him a watch, explaining he got it "from a dead person".{{sfn|Sullivan|2000|p=71}}{{efn|Cram also informed investigators in this interview Gacy had allowed him to retain a driver's license belonging to a [[DeVry University]] student he found in Gacy's garage in approximately February 1977 so he could engage in underage drinking. According to Cram, Gacy also informed him this identification belonged to a deceased individual.}}

Investigators conducted a formal interview of Rossi on December 17. He informed them Gacy had sold him Szyc's vehicle, explaining that he had bought the car from Szyc because he needed money to move to California. A further examination of Gacy's Oldsmobile revealed a small cluster of fibers in the trunk, suspected to be human hair. That evening, three trained [[Search and rescue dog|search dogs]] were used to determine whether Piest had been present in any of Gacy's vehicles. One laid on the passenger seat of Gacy's Oldsmobile in what the dog's handler informed investigators was a "death reaction", indicating Piest's body had been present.{{sfn|Sullivan|2000|pp=84–93}}

That evening, Gacy invited detectives Albrecht and Hachmeister to a restaurant for a meal. Early on December 18, he invited them into another restaurant where, over breakfast, he discussed his business, his marriages and his clowning. During the conversation, Gacy remarked: "You know{{nbsp}}... clowns can get away with murder."{{sfn|Sullivan|2000|p=90}}{{sfn|Linedecker|1980|p=226}}

By December 18, Gacy was beginning to display signs of strain from the constant surveillance: he was unshaven, looked tired and anxious and was drinking heavily. That afternoon, he drove to his lawyers' office to prepare a $750,000 [[civil suit]] against the Des Plaines police, demanding that they cease their surveillance.{{sfn|Sullivan|2000|pp=99–104}} The same day, the Nisson Pharmacy photo receipt found in Gacy's kitchen was traced to 17-year-old Kimberly Byers, a colleague of Piest at Nisson Pharmacy. Byers stated that she had borrowed Piest's parka earlier in the evening and had placed the receipt in the pocket just before she returned the coat to Piest as he left the store.{{sfn|Sullivan|2000|pp=123–127}}<ref>{{Cite web|url=https://www.harpersbazaar.com/culture/features/a24269889/john-wayne-gacy-kim-byers-lund-interview/|title=A Serial Killer, a Receipt, and My Mom: Haunted by the Murder of 33 Boys|date=October 31, 2018|website=harpersbazaar.com|access-date=March 10, 2024}}</ref>