Since his execution 15 years ago, the shrunken, sliced, and preserved brain of John Wayne Gacy has been stored in a Ziploc bag in the basement of a home in Chicago, Illinois. Dr. Helen Morrison, who spent approximately 50 hours with Gacy prior to his trial, sought to identify any physical factors that could explain his heinous acts of murdering 33 boys and young men. After testifying in his defense that he was mentally ill and legally insane, Morrison, following Gacy's execution, received approval from his surviving family members to remove his brain for study.

During Gacy's autopsy, his brain was extracted and entrusted to Dr. Morrison, where it has been kept at her home. Despite hopes that studying Gacy's brain might reveal insights into his monstrous actions, research has shown no abnormalities that could shed light on his brutal behavior.

“Clowns can get away with murder.” - Gacy

Gacy was a member “Jolly Joker” a Chicago clown club, and frequently performed at children’s parties, charity fundraisers, and other events as his alter egos “Pogo the Clown” or “Patches the Clown.” Pogo, he said, was a "happy clown", whereas Patches was described as "more serious."

Gacy rarely made any money during his appearances, and has even admitted that acting as a clown allowed him to "regress into childhood."

His creepy, overweight, homemade clown personas have led to his nickname the “Killer Clown.” He even donned the costume during the sexual assault of one of his victims.

Gacy's house also had photos of sad-faces clowns on the walls.

"When you clowned, you're hiding your image. There are things you could do that you couldn't do as a person." - Gacy

Gacy would lure his victims into his home with lies, or force them in by gunpoint. He played Russian roulette with at least on victim who happened to survive the ordeal.

In 1979, during an extensive search, a .32‐caliber automatic was found buried in the concrete steps leading to Gacy's house. It was a surprise to investigators, who believed that most if not all of the victims were strangled.

In 1971, Gacy started a construction business called PDM Contractors - PDM stood for Painting, Decorating, and Maintenance. He employed mostly high school students and young men, many of whom he would proposition for sex, sometimes under the threat of violence.

The company served as a convenient hunting ground, as he could lure potential victims with the promise of a high-paying job. Gacy frequently looked for the vulnerable — young men whose disappearances were initially explained away by police as runaway cases.

"I should never have been convicted of anything more serious than running a cemetery without a license." - Gacy

Towards the front of his house at 8213 West Summerdale Avenue, in Norwood Park, Illinois, in a living-room closet, Gacy had a trapdoor leading down into a dark, dirt-floored crawl space. A disgusting, putrid smell emanated from the hole: the smell of sewage and decay. When investigators told Gacy they planned on digging up his crawl space, he immediately cooperated and drew them a map pinpointing all the bodies. Of his 33 known victims, 26 were found underneath the house.

Gacy had covered his victims with quicklime to speed up the decomposition process, but once officers dug below that, the odor was so putrid, they described it unlike they had ever encountered before. Gacy had buried the bodies all around the outer edges of the crawl space - some of them he put one on top of the other.

Because it was so wet and moist, officers had to dig with a very small gardening tool and use their hands. They didn't want to displace any bones or teeth to disrupt any means of identification. They found corpses whose heads had detached themselves from the spine because of the way Gacy strangled them.

When the officers first went down into the crawl space, they observed dark, murky puddles filled with hundreds of thin red worms - about two inches long. When flashlights were shown on them, burrowed into the soft mud.

Detectives suspected they were feeding on human remains, and so they started to slowly shovel into the mud. Soon after, they hit an arm bone.

The first bone that detectives found in Gacy's crawl space was an arm bone, and after that, they kept finding femurs -- three left femurs in succession. This signified to them that there were a lot of victims they were going to uncover.

A receipt from a film developing purchase became a key component to capturing Gacy...

A 15 year old honor student told his mother he would be speaking with a contractor about some promising employment opportunity. He was reported missing later that day. Investigators learned the identity of that contractor — John Wayne Gacy — and questioned him about the teen’s whereabouts. They also discovered Gacy’s previous conviction of sexual abuse, for which he was currently on parole, and wanted to investigate him further. They executed a search warrant at Gacy’s home, where they come across some interesting items: several police badges, a syringe and hypodermic needle, handcuffs, books on homosexuality and pederasty, pornographic films, capsules of amyl nitrite, a dildo, a two-by-four with two holes drilled into each end, bottles of Valium and atropine, several driver's licenses, a blue hooded parka, underwear too small to fit Gacy, a class ring engraved with the initials J.A.S. And in a trash can located in Gacy’s kitchen, investigators found a Nisson Pharmacy photo processing receipt - the same pharmacy where the missing teen worked.

One of Gacy's most vile ways of binding his victims was convincing them to allow him to handcuff them, under the pretense that it was part of a magic trick. He would at first perform the 'handcuff trick' on himself: putting the pair on his own wrists, behind his back, and then free himself with the key which he’d concealed in his hand. He’d then tell his victim that he would show them how the trick worked, getting them to put on the handcuffs. When they couldn't free themselves, Gacy would tell his victim that the trick was to have the key.

Once his victim was restrained, Gacy began his rape and torture. He would be by straddling his victim's chest and force the victim to fellate him. He would then burn them with cigars, make the victim imitate a horse as he sat on their back and pulled on makeshift reins around their necks, and violate them with objects such as dildos and prescription bottles.

Gacy liked to drive around in his car, and find young victims to talk to while posing as a policeman. He would flash a fake sheriff's badge, and lure them into his vehicle. He would then force them to perform oral sex.

Gacy enticed one of his victims into his car by offering him marijuana. Once inside, Gacy used chloroform to render him unconscious, then drove him to his house, handcuffed him and sexually attacked him before letting him go.

Eventually, while under police surveillance, Gacy hands a package containing marijuana to a clerk at a gas station. Police then follow Gacy, and arrest him.

Gacy's main method of murder was strangulation: he would wrap a rope around his victims’ neck, tie it to a hammer, and twist and twist until they suffocated.

During his early adult years, Gacy worked at Palm Mortuary as an attendant, frequently witnessing morticians perform the embalming process on the deceased. Gacy frequently slept in a cot behind the embalming room. One evening after all the workers had gone home, he climbed into the coffin of a deceased teenage male, embraced and caressed the body, and laid there with the corpse.

When Gacy was immediately out of college, the Nunn-Bush Shoe Company hired him as a manager trainee. He soon started to take on a sales role. Within weeks of working as a salesman, his boss promoted him to the department manager.

Once Gacy got his victims back to his house, he would handcuff them or tie them up, usually after intoxicating them with alcohol or knocking them out with chloroform. His various method of torture included using a fire poker on them, dripping hot melted candle wax on their bodies, repeatedly drowning them in his bathtub, or by placing them in a homemade "rack". As a show of dominance, he would urinate on his victims. Gacy would rape his victims both before and after killing them, keeping the bodies around for a day or so.

One of the victims who worked for Gacy's construction company informed his family that Gacy had him "dig trenches for some kind of (drain) tiles" in his crawl space.

Eventually when on trial, Gacy testified that he had only dug five of the victims' graves in his crawl space and had had employees dig the remaining trenches so that he would "have graves available."

Once Gacy would have his victim's incapacitated, he would often stick paper towels or clothing - such as a sock or even their own underwear - in their mouths to muffle their screams, causing them to fatally asphyxiate.

Even after the case against Gacy was closed, eight victims remained unidentified and remained so for decades. In 2011, the Cook County Sheriff's office reopened the investigation, and used teeth to extract DNA. They used DNA technology and forensic genetic genealogy to identify three, finally giving closure to families.

Gacy was brazen enough to lure victims to his house during daylight, often in public places like a bus station. This included his very first victim who he found at Chicago's Greyhound Bus Terminal.

Gacy killed his first victim by stabbing him in the chest with a kitchen knife. Gacy subsequently buried him in his crawl space and later covered the youth's grave with a layer of concrete.

In an interview, Gacy stated that immediately after his first murder, he felt "totally drained," yet remarked that he had experienced orgasm as he made the kill: "That's when I realized that death was the ultimate thrill."

Gacy lured a 19-year-old college student from a Chicago bus stop to his house where he raped and tortured him. One of his torture methods involved dunking his head repeatedly in a bathtub until he passed out, and performing fake executions with a gun loaded with banks. The victim was in so much pain he begged Gacy to kill him, but Gacy let him go and warned him not to tell anybody. However, the young man reported him to the police. But when officers investigated, Gacy said it was a consensual “sex slavery” meet-up. The police believed him, and Gacy continued to kill.

Gacy was dating a co-worker named Marlynn Myers, and her father had purchased three Kentucky Fried Chicken restaurants in Waterloo, Iowa. He wanted someone he could trust to manage them, so he hired Gacy.

Gacy was a member of his local chapter of the Jaycees, and at their meetings, Gacy would bring fried chicken. He insisted upon being given the nickname "Colonel".

Gacy’s last meal consisted of a dozen deep-fried shrimp, a bucket of KFC’s original recipe chicken, French fries, a pound of strawberries, and a bottle of diet Coke.

Defense attorneys wanted to observe Gacy’s brain waves while he drank, because Gacy claimed to blackout when drinking, not remembering his actions during these times. The defense set out to see if alcohol turned Gacy into a killer. Gacy, who had not had a drink in six months, was given six shots of J&B scotch over an hour and 15 minute period, 15 minutes apart. Psychiatrists looked to see if a physiological change in the function of the brain occurred that would trigger a level of impaired behavior.

In Gacy's case, there was no change.

Gacy has been described as a homophobic homosexual: refusing to admit that he was gay, but told his wives he was bisexual. He termed men who enjoyed sex with men "fruit pickers," but yet only lured young men into his home to assault and kill. In secret, he was a sexual and homicidal predator. When investigators searched his home, they found pornography, shackles and two books titled “Gay Love Letters” and “Pretty Boys Must Die.”

After weeks of surveillance, investigators had a warrant to dig. One of the techs moved a corner of the crawl space where he noticed dark, murky, and foil smelling puddles - filled with hundreds of slippery red worms. He suspected they were feeding on human remains. He lowered his shovel into the mud and hit an arm bone. In the next 10 days, the remains of 28 teenage boys and young men were found.

Gacy would torture his victims in vile ways, including: dripping hot melted candle wax on their bodies, repeatedly drowning them in his bathtub, using a fire poker in various ways, or by placing them in a homemade "rack". Disgustingly, he would urinate on his victims, and rape his victims both before and after killing them, keeping the bodies around for his pleasure before burying them.

Gacy fancied himself a magician of some sorts: both by publicly dressing as either Pogo or Patches the Clown, and privately using his "magic tricks" as deceptions to bind and handcuff his victims.

Gacy's favorite way to subdue and eventually murder his victims was strangulation, most of the time by tying a rope tourniquet around their neck and gradually tightening it with the handle of a hammer. He referred to this as the "rope trick", often informing his victim, "This is the last trick."

Many of the bodies were found with the tourniquet Gacy used to strangle them, still knotted around their neck.

Gacy's second wife, Carol Hoff, lived with him in the home where he buried his victims. Throughout the summer of 1972, she noticed a repugnant smell that seemed to come from the crawl space. Around the area was a swarm of flies, and suspected that perhaps there were decaying dead mice. When she questioned Gacy about this, he blamed it on runoff odor from a broken sewer pipe. He spread lime in the crawl space to try and control it, but the odor got worse.

Carol had left on a trip, and upon her return, Gacy informed her that he had poured concrete in the crawl space to get rid of the smell. The flies disappeared, but the smell was still there, although a bit less pungent. Carol told others that she sometimes saw Gacy go into the crawl space with a fifty-pound bag of lime, to spread over the damp ground to try to control the smell.

Gacy would sometimes strangle his victims using a plank of wood, sometimes while he sexually assaulted them with sex toys.

Gacy attended four different high schools, but dropped out before completing his senior year. He took off to Las Vegas, Nevada, and lied about his age to get a job as an ambulance driver at the Palm Mortuary Memorial Park (min. age was 21). When the manager learned the truth, he offered Gacy an alternative position as a mortuary assistant. His job included moving corpses and material from the hospital to the funeral home.

Gacy burned his victims with cigars, as well as making his captive imitate a horse as he sat on their back and pulled on makeshift reins around their necks.