A 35-year-old man from Watford died after overdosing on an "unusually high strength" heroin the first time he was injected with the drug.
A text message warning of the drug's potency might have changed the course of events leading up to the death of Kristen Johansen, of Strangeways, but it was left unread, the inquest was told.
It also heard the confusion around how Mr Johansen came to be injected with the heroin, as he was right handed and the injection was in his right arm.
Mr Johansen had been drinking with two friends Ben Kempster and Anthony Stilwell on the night of November 5, 2013.
During the evening Mr Kempster purchased £20 worth of heroin and drug paraphernalia and brought it back to Mr Stilwell’s flat in Hudson Close, where the three often met and drank alcohol together.
Deputy Coroner Graham Danbury heard police later discovered a text message on Mr Kempster’s phone from the heroin supplier warning the drugs were more powerful than usual - the message was unread.
Mr Kempster told the court he took the heroin first, that it affected him very quickly and that when he came to his senses sometime later and checked on his friends he found Mr Johansen was white and not breathing.
Deputy Coroner Danbury read a statement Mr Kempster gave to police, it said: "All I did was cook up the heroin, I didn’t give any heroin to Kris."
Mr Kempster said Mr Johansen repeatedly asked for heroin, and he had told his friend of 12 years it was not a good idea for him to inject the drug as he had never done it before.
Answering questions from Mr Johansen’s mother, Mr Kempster said: "I’ll be honest, it was the worst night of my life."
Mr Stilwell said the amount of heroin each of the friends took was very small, but it affected them as if it was £50 worth of the substance.
He said: "I didn’t know it was his first time. It was such a small amount of heroin."
During the inquest, Mr Johansen’s mother said she remembered the day vividly and that she did not hate the witnesses, she only wanted to find out the truth of what happened to her son.
Mr Johansen’s father and sister were also present at the inquest.
A post-mortem concluded Mr Johansen had died from a mix of heroin and alcohol intoxication.
The deputy coroner ruled the cause of death was non-dependent misuse of heroin.
He said: "I don’t think you will ever find you’ll have a clear picture of what happened in Mr Stilwell’s flat that night.
"Kristen Johansen was injected with a quantity of heroin, which appears to have been of unusually high strength.
"Kristen Johansen’s death came about directly from the combination of alcohol and drugs.
"I accept he was not a regular drug user, there is no evidence of previous injection.
"Clearly he had a long standing problem with alcohol.
"But I am satisfied he wasn’t in any sense dependent on heroin."