A civil engineer who died from acute alcohol poisoning after downing a cocktail of shots had challenged friends to drinks races on nights before, a court was told.
Hotel staff are accused of serving Graham Parish the mix of spirits in one glass, which rapidly pushed his blood alcohol level up.
Nenagh Circuit Court was told tests showed the amount of alcohol in the British man's blood was above the average taken from a study of 175 similar deaths.
Bar manager Gary Wright and barman Aidan Dalton have pleaded not guilty to the manslaughter of Mr Parish in the Hayes Hotel in Thurles, Co Tipperary, on June 30, 2008.
His colleague, Simon Turner said Mr Parish started racing pints before he had "a cocktail of mixed spirits" which he alleged was handed over by bar staff.
"It was his suggestion to challenge people to race to drink a half-pint of spirits to a half pint of lager," Mr Turner told a jury and Judge Thomas Teehan.
The court heard vodka, gin, baileys, brandy and possibly a Jagermeister were in the glass, with a till receipt showing eight shots of spirits costing €30 were bought at 10.40pm.
Within minutes, Mr Parish had slumped off his bar stool and was carried to a conference room on the first floor of the hotel by four friends - where his dead body was found by a night porter shortly after 6am the following morning.
Mr Turner told detectives Mr Parish had previously challenged people to a drinks race.
"I have been out with him several times over the course of the seven years I knew him," said the steel erector, who worked alongside Mr Parish at Skipton-based Reliant Installations Ltd.
"He always wanted to show people how quick he could drink pints of Guinness. I have seen it a few times but I think it was done in his student days.
"He was at the University of Derby. He came to work with us on his summer holidays.
"I have seen it before but not with spirits, only with Guinness."
Daniel Watson, an electrician from Snaith near Doncaster, told the court he was drunk on the night and had taken on Mr Parish's challenge to down a pint of Guinness in two or three seconds, but could not manage it.
Mr Parish, a father-of-two, was from Calder Terrace in Lomeshaye village near Nelson, east Lancashire.
His parents David and Julie and sister Jess have travelled to Ireland for the trial at Nenagh Circuit Court.
The landmark case is the first of its kind under liquor liability laws in Ireland.
If convicted, Mr Wrigh (aged 34) and Mr Dalton (aged 28) who are both from Kilfithmone, Borrisoleigh in Co Tipperary, face up to life in jail.
Pathologist Stephen Finn determined Mr Parish died from acute alcohol intoxication based on the amount of ethanol found in his blood and urine.
Tests showed 375mg of alcohol was in his blood - above the average of a Belfast study of 175 deaths from acute alcohol intoxication which recorded a mean average of 355mg.
"These are very high levels of alcohol and ethanol in blood and urine," added Dr Finn.
Vomit found on Mr Parish's lip had not entered his wind pipe and did not contribute to his death.
Dr Joseph Tracey, the former clinical director of the National Poisons Information Centre, Beaumont Hospital, Dublin, said the blood alcohol level was at the lower end of the fatal dosage scale.
But he calculated 10 shots taken rapidly would have dramatically increased the level - pushing a person into unconsciousness.
"I believe this man died from acute alcohol poison," he added.
The case continues.