Detectives arrested a 47-year-old man on suspicion of murder and later charged him with manslaughter after the death of 39-year-old Jeffrey Howarth, of Gannet Close, Castleford.
Wakefield Coroner's Court heard the manslaughter charge was later dropped after a post mortem and toxicology analysis revealed Mr Howarth, who had a history of alcohol abuse, was the equivalent of more than four times the drink drive limit and had taken heroin.
The 47-year-old man who had originally been charged with manslaughter was later charged with assault, which he admitted when he appeared at Leeds Crown Court.
Detective Sergeant Richard Smith, of West Yorkshire Police's Homicide and Major Enquiry Team, told the inquest a visitor to Mr Howarth's home on Gannet Close alerted emergency services just before 2pm on September 8 2016 after noticing he had been the victim of an assault and had head injuries.
Det Sgt Smith said police and paramedics attended, but Mr Howarth did not want to go to hospital or cooperate with police.
The inquest heard a neighbour called at Mr Howarth's home just before 8pm that night and found him slumped on the toilet and unconscious.
The neighbour called for an ambulance and Mr Howarth was taken to Pinderfields Hospital at Wakefield, where he was declared dead just after 9pm that night.
Det Sgt Smith said: "It was a full blown murder enquiry all the way through until we got the results of the post mortem."
Area Coroner Jonathan Leach read a statement from Home Office pathologist Dr Kirsten Hope who carried out the post mortem and said Mr Howarth had injuries including rib fractures and two black eyes.
Dr Hope said in the statement that toxicology result showed he had drunk a large amount of alcohol and had taken heroin shortly before his death.
Dr Hope concluded that Mr Howarth died of alcohol and heroin toxicity and that the injuries he sustained in the assault did not play a part in his death.
Mr Leach recorded a verdict of alcohol and drug related death.
After the inquest hearing Mr Howarth's sister Diane Simmonds, 53, of Featherstone, said her brother, a fomer fork lift truck driver at Linpac in Featherstone, had battled alcohol addiction for a number of years.
She said: "He started drinking in his twenties. He used to play snooker at Green Lane WMC. It was just social drinking and then before you know it, it was every day.
"He was dependent on it and couldn't go a day without it."
Miss Simmonds said her brother had attempted to stop drinking and had been attending adult treatment service Turning Point in Castleford before his death.