Trengove was charged over a tackle on Adelaide's Patrick Dangerfield during Melbourne's 96-point win on Sunday, which left the young Crow concussed after his head hit the ground.
The young star could have accepted a two-match ban had he opted to plead guilty, but instead will now miss Melbourne's clashes with North Melbourne, St Kilda and Carlton.
Player advocate Iain Findlay argued that Trengove's tackle was within the rules and spirit of the game, and that he had not used unreasonable or excessive force in bringing Dangerfield to ground.
Demons tackling coach Kelly O'Donnell testified that Trengove had affected the tackle exactly as the club teaches, and that in grabbing his opponent's arm he had used a reasonable tactic to try to dispossess Dangerfield of the ball.
Bio mechanist Dr Kevin Ball, a former assistant coach at Fremantle now employed by Melbourne, said that the force with which Dangerfield hit the ground was increased because he was making a kicking motion as he was tackled, which threw him off balance and quickened his fall.
Ball also argued that Trengove had his feet knocked out from under him as he completed the tackle, causing him to lose balance and have less control as he tackled Dangerfield to the ground.
But tribunal counsel Andrew Tinney SC suggested that by grabbing hold of Dangerfield's arm and keeping hold of it throughout the tackle, Trengove had not exercised his duty of care to his fellow player's safety.
Tinney also argued that Trengove used a level of force above what was required to achieve his aim of dispossessing Dangerfield or stopping him from disposing of the ball.
He read a medical report from the Adelaide doctor stating that Dangerfield was concussed as a result of the incident, was unable to return to the field of play, and continues to have his cognitive function monitored daily.
The tribunal upheld the MRP's initial ruling that the tackle constituted negligent conduct, medium impact and high contact, a total of 325 demerit points.
