Three years before Gacy was arrested, and before any of his murders had even come to light, Detective Bill Dorsch lived just around the corner from the apartment building at the corner of Elston and Miami avenues.
Gacy worked as the building's caretaker, and Dorsch recalls one morning when he was passing by and saw Gacy with a shovel in his hand.
"I said to John, 'John, what the heck? It's 3 o'clock in the morning. What are you doing?' John sort of laughed, and he walked over close to me with the shovel, standing by the door and said, 'Well, Bill, you know me. Not enough hours in the day. You've got to get it done."
Dorsch said he didn't think anything of it at the time, but when Gacy was later revealed as a serial killer, he came forward to his colleagues that there may be more bodies buried on the property. After all, Gacy himself estimated that he killed 45 men, but only 33 bodies were ever found.
"I told them, 'You should talk to the people in the building," he explained. "And that's the way I left it."
Amid the multitude of tips flooding in at the time, Dorsch's story went ignored until 1998 when a dig on the property turned up empty.
To this day, however, Dorsch maintains that dig was less than thorough. He says radar evidence he gathered with a professional scanning firm identified 17 so-called "anomalies" underground. Many of them were ignored by police, Dorsch said.
"Every anomaly that they found in that scan should be looked at, not just two of 17," he said.
For the first time, Dorsch is publicizing a 1998 interview that he and a colleague did with a former resident of the building who also believes there are bodies there.
"If I don't tell this story, even if nothing is done with it, I've got it out there. I've marked it like the pyramids," he said.
Lynn Troester, who lived in the building from 1967 to 1975, said she witnessed Gacy digging a series of large trenches in the front yard of the property, not the backyard where police searched.
"He would dig," Lynn Troester said in the interview. "No pattern. He would just dig. And then leave it, and all of a sudden there'd be plants."
In a statement, the Chicago Police Department said it stands by the investigation and findings as reported in 1998. The investigation remains closed.