But Magistrate Kieran Gilligan discharged Gleeson on three charges after forensic physician John Gall conceded he could not say whether those children's injuries could be considered serious. 

The prosecution also withdrew another charge at the start of Tuesday's hearing.

Dr Gall, who gave evidence to Melbourne Magistrates Court from the United Kingdom, said he had not received follow-up medical material on the students' injuries. 

Dr Gall told the court he therefore could not say whether they were protracted injuries, a legal test that needs to be met for an injury to be considered serious. 

Forty-five students were on the school bus at the time of the Eynesbury collision, with two of the students requiring full or partial amputations as a result of their injuries. 

After the crash, Gleeson told police he hit the brakes as soon as he saw the bus' brake lights on but he didn't have enough time to avoid the collision. 

He said he noticed flashes of sunlight coming through the trees on his right-hand side in the lead-up to the crash. 

The bus driver, Graham Stanley, told the court he had his indicator on for about 150 metres before the crash and he slowed to a near or complete stop to turn.

Another driver disputed his claims, with David Woods telling the court he did not see any brake or indicator lights before the collision. 

Detective Senior Constable David Morris on Tuesday told the court he believed Mr Stanley was "blameless".

Det Morris did concede officers never asked the bus driver when he started slowing down or indicating, noting they only took one statement from Mr Stanley on the day of the crash. 

Gleeson remains on bail to appear at the Victorian County Court for a directions hearing on May 22.