Senior loyalist Ihab Shoukri had been smoking heroin before he died, a doctor has told an inquest.
The Ulster Defence Association member, 34, was discovered by his partner slumped on his sofa in north Belfast. He had been due to become a father.
Belfast coroner Brian Sherrard found he died from a cocktail of drugs in 2008. This was disputed by his family who drew attention to his history of suffering fits. His brother and fellow loyalist Andre was in court but left before the end of proceedings.
Mr Sherrard said: "The use of illicit drugs in our society has become really endemic and has led to the premature deaths of many young people with their full lives ahead of them."
Shoukri, from Grainon Way, Rathcoole, had been released from prison in the summer of 2008 after admitting to being a member of the UDA. He watched televised boxing with friend Stephen Green at home before his girlfriend discovered him not breathing in the early hours of the morning on November 23.
Mr Green denied knowing of any drug use and Shoukri's partner Emma Ritchie said she was also unaware of anything illegal. There was no evidence of substance abuse in the house following the death, police said. Ms Ritchie said he had been "terrible" on the day of his death but, against her advice, played football.
He suffered 15 seizures between 2003 and 2006 but doctors had been unable to determine the cause and he had not been attending appointments. Assistant state pathologist Dr Peter Ingram discovered morphine, codeine and diazepam in his blood after death and said the composition of the morphine led him to conclude it had been as a result of heroin use. There was no evidence of injection, so he said it was likely it had been smoked.
"It was heroin and not pure morphine," he said. He added: "It would seem reasonable to conclude that it was the effect of these drugs which led to the development of pneumonia."
He said if the victim had died from an epileptic fit there would probably have been little signs as to cause of death and no pneumonia. In Shoukri's case there would have been a gradual loss of consciousness from the effects of the drugs and the onset of pneumonia, the medic added.
Ms Ritchie said after the football match he suffered flu-like symptoms and was lethargic with heavy eyes. "He just constantly worried all the time but he would never let you know," she added. The coroner found that he died from pneumonia due to the effects of morphine, codeine and diazepam.