Ireland will have to plan to face New Zealand in Saturday's World Cup quarter-final without Bundee Aki after the powerful centre was ruled out of the remainder of the tournament through suspension.
The 29-year-old was sent off for a high tackle on UJ Seuteni in Ireland's 47-5 win over Samoa on Saturday and has been hit with a three-match ban.
The committee did not accept that there was sufficient evidence of a sudden drop in the ball carrier's height, and while it acknowledged that the tackle occurred quickly, the tackle was high.
It also rejected the argument there was a low degree of danger.
Crucially, the committee found that there were "no clear and obvious mitigating factors".
The IRFU have 48 hours from the publication of the written decision in which to decide whether or not to appeal the decision.
In a statement issued following the hearing, the Irish management said they are "disappointed with the outcome of Bundee's hearing and will review the Judicial Committee's written report once received".
The six-week entry point was reduced by the maximum permitted three weeks having taken into account the player's good disciplinary record, which equates to three matches in the context of Rugby World Cup 2019.
"On the balance of probabilities, the committee did not find that the referee's decision was wrong and the red card was upheld," a World Rugby statement read.
It confirmed that Aki must sit out the next three games, whether for country or province.
"Aki will miss Ireland's quarter-final against New Zealand on 19 October, the semi-final and final of Rugby World Cup 2019 should Ireland qualify, or should Ireland not qualify for these games, the player’s next club match or matches with Connacht in the Pro 14 on his return from international duty."
Ireland boss Joe Schmidt said Aki was "devastated" to have been sent off against his fatherland Samoa in Saturday's seven-try win in Fukuoka.
The IRFU flew Derek Hegarty, a solicitor and partner in William Fry's law firm, to Japan to represent the Connacht centre at the hearing chaired by Adam Casselden QC (Australia).
Samoa head coach Steve Jackson immediately pledged to make any possible representation to World Rugby, in the hope Aki would not receive any further punishment than his red card.
Follow Ireland v New Zealand on Saturday 19 October (kick-off 11.15am) via the live blog on RTÉ.ie/Sport and the News Now App, watch live on RTÉ2 or listen to live match commentary on RTÉ Radio 1.