A three-man disciplinary panel in Cardiff studied the circumstances surrounding the alleged incident and concluded that Matawalu's teeth had probably come into contact with O'Callaghan's arm, causing injury, but that the contact was accidental and therefore not an act of foul play.
The clash had occurred in the final few minutes of a fractious contest in which Glasgow surrendered their unbeaten RaboDirect PRO12 record this season. The first indication came when the Irish lock complained to referee Ian Davies he had been bitten, holding his arm out to show a bite mark. Davies rejected the complaint, saying that the citing commissioner would take the matter up.
The commissioner, Scotland's Rob Flockhart, did so, starting a process that led to Roger Morris and Rhian Williams of Wales and Italy's Marco Cordelli studying the accusation for three-and-a-half hours before ruling the evidence was not strong enough.
Biting is viewed as one of rugby's most heinous offences and attracts heavy punishments. Had Matawalu been found guilty, his offence would have been viewed at the lower end of the scale of severity, but he would still have been banned for up to three months. With Chris Cusiter and Henry Pyrgos in the Scotland squad, Gregor Townsend would then have been obliged to call up players from RBS Premiership sides to provide cover in the scrum-half position.
Privately, Warriors officials are furious over O'Callaghan's role in the affair. Aside from his attempt to influence the referee, it has also been suggested that O'Callaghan provoked Matawalu when they clashed in a ruck moments before the alleged bite.
Conor Murray, the Munster scrum-half, also walked away from the hearing a free man. It was agreed he had been guilty of an act of foul play when he struck an opponent, but the panel ruled that the offence would not have merited a yellow card had it been picked up by the referee, so no further punishment was imposed.