Following an investigation, Las Vegas police concluded there were no signs of foul play and declared Liston’s death a heroin overdose. “It was common knowledge that Sonny was a heroin addict”, said Sgt. Caputo, one of the investigating police officers, “The whole department knew about it.” The date of death listed on his death certificate is December 30, 1970, which police estimated by judging the number of milk bottles and newspapers around the front door of the property. Coroner Mark Herman said traces of heroin by-products were found in Liston’s system, but not in amounts large enough to have caused his death. Also, scar tissue, possibly from needle marks, was found in the bend of Liston’s left elbow. The toxicology report said his body was too decomposed for the tests to be conclusive. Officially, Liston died of lung congestion and heart failure. He had been suffering from hardening of the heart muscle and lung disease before his death. Liston had been hospitalized in early December, complaining of chest pains.
Liston was buried at Paradise Memorial Gardens in Las Vegas, Nevada. The grave’s marker-plate bears the dedication: ‘A Man’.
Theories regarding the circumstance of Liston’s death
Sgt. Dennis Caputo of the Clark County Sheriff’s Department was one of the first officers on the scene. He found a quarter-ounce of heroin in a balloon in the kitchen, and a half-ounce of marijuana in Liston’s pants pocket, but no syringes or needles. Some found it suspicious that authorities could not locate any drug paraphernalia that Liston presumably would have needed to inject the fatal dose, such as a spoon to cook the heroin or a tourniquet to wrap around his arm. But former Las Vegas police Sgt. Gary Beckwith said, “It wasn’t uncommon for family members in these cases to go through and tidy up … to save family embarrassment.”
Many people who knew Liston insisted he was afraid of needles and never would have used heroin. “He had a deadly fear of needles”, said Davey Pearl, a boxing referee and friend of Liston’s. “There was nothing Sonny feared more than a needle. I know!” said Liston’s Philadelphia dentist, Dr. Nick Ragni. “He was afraid of needles”, echoed Father Edward Murphy. “He would do everything to avoid taking shots.” According to Liston’s trainer, Willie Reddish, Liston cancelled a planned tour to Africa in 1963 because he refused to get the required inoculations. Liston’s wife also recalled that her husband would refuse basic medical care for common colds because of his dislike of needles.
“The month before he died, some guy ran into Sonny while he was making a left turn. He had a whiplash, so they took him to the hospital”, said boxing trainer Johnny Tocco. “He said: ‘Look what they did!’ and he was pointing at some little bandage over the needle mark in his arm. He was more angry about that shot than he was about the car wreck. A couple weeks later, he was still complainin’ about that needle mark. To this day, I’m convinced that’s what the coroner saw in his exam—that hospital needle mark.”
Some claim Liston was murdered. There are several theories as to why: (1) Publicist Harold Conrad and others believed Liston had been deeply involved as a bill collector in a loan-sharking ring in Las Vegas. When he tried to muscle in for a bigger share of the action, Conrad surmised that his employers got him very drunk, took him home and stuck him with a needle. (2) Professional gambler Lem Banker insists that Liston was murdered by drug dealers with whom he’d become involved. Banker said he was told by police that Liston had been seen at a house that would be the target of a drug raid. Banker said, “Sheriff [Ralph] Lamb told me, ‘Tell your pal Sonny to stay away from the West Side because we’re going to bust the drug dealers.'” Banker later learned that the police told Liston the same thing to his face. He apparently was at the dealers’ house shortly before they got busted. Because of that, the dealers may have thought Sonny ratted on them and they shot him with a hot dose as retribution. (3) The mob promised Liston some money to throw the second Ali fight, but they never paid him. As the years passed and Liston’s financial situation worsened, he got angry and told the mob he’d go public with the story unless they gave him the money. That got him killed. (4) Liston was supposed to take a dive when he fought Chuck Wepner six months earlier, and killing him was payback for his failure to do so.
Some believe the police covered up what happened.[who?] On January 1, Liston’s wife called Johnny Tocco and said she had not heard from her husband in three days and was worried. A few years before Tocco died, he allegedly told his good friend Tony Davi that he went to Liston’s house and found the door locked and his car in the driveway. Tocco called the police, and they broke into the house. Tocco said that the living room furniture was in disarray, but the house did not yet smell of death. He said they found Sonny lying on his bed with a needle sticking out of his arm. Johnny left the house before the police did. “Johnny wasn’t a braggart,” Davi told Liston biographer Paul Gallender. “He told me in the strictest confidence, but it was like he wanted to get it off his chest.” Gallender claimed, “A lot of officers knew Sonny was dead before Geraldine returned home on January 5, but they chose to let him rot.”