Lawyer Ian Hill QC grilled Detective Senior Constable Cliff Pickett, of the Victoria Police sporting integrity intelligence, during the second day of an online committal hearing on Wednesday for Weir and McLean, who each face charges of animal abuse and conspiracy to defraud stewards.

Mr Hill suggested the detective failed to provide an expert witness with the majority of video footage taken from Weir's Warrnambool stables between October 25 and November 13, 2018.

He said clinical ethologist and horse trainer Andrew McLean only covert viewed footage from the stables on one day - October 30, 2018 - and not the remaining 18 days.

Police allege video footage from that date showed an electric shocking device being used on horses on a treadmill.

Detective Senior Constable Pickett said there was about 460 hours of footage in total and it was not "feasible or relevant" to show the expert witness all of it.

Mr Hill suggested that the footage between October 25 and November 13, 2018, showed horses "simply being exercised on the treadmill at Warrnambool", in which the investigator replied: "Apart from one occasion where I saw them being tortured".

Detective Senior Constable Pickett agreed the bulk of the footage was not incriminating.

Mr Hill accused the investigator of "deliberately (choosing) to withhold exculpatory evidence from your own expert".

Exculpatory evidence is evidence favorable to the defendant in a criminal trial that exonerates or tends to exonerate the defendant of guilt.

Detective Senior Constable Pickett said he did not withhold the footage but rather "decided not to show" the behavioural scientist.

Mr Hill pressed the investigator on the "cues" which police allege the trainers used in training in an attempt to replicate on race day, including whistling and the wearing of blinkers.

Detective Senior Constable Pickett said there were no reports of whistling in the races that followed the alleged offending on October 30, 2018, including the Melbourne Cup, Sandown Cup and the Lexus Stakes.

He agreed Weir-trained horse Yogi did not wear blinkers in the Lexus Stakes race despite allegations of the horse wearing them during training at the Warrnambool stables.

He also agreed he did not interview any of the jockeys in the races, except those who rode the Weir/McLean-trained horses.

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He said those jockeys were not forthcoming in the police investigation.

Detective Senior Constable Pickett said the expert witness did not view any footage from the races.

He said the witness was paid "about $8000" for his work.

The court heard cameras were installed at Weir's Warrnambool stable from October 25 to November 13, 2018, and at his Ballarat stable between November 1 and 12.

Mr Weir became aware of one of the cameras at the Ballarat premise around November 12, the court was told.

Earlier in the hearing, senior constable Matthew Don, who investigated the case while he was working in the sporting integrity unit, was interrogated in relation to notes he made on October 11, 2018 which suggested that surveillance cameras were not working.

McLean's lawyer Jason Gullaci asked the senior constable whether his notes referred to cameras being in operation prior to October 23, 2018.

Senior Constable Don said he had "no recollection" of the notes but he believed they were referring to potential avenues of the investigation, rather than the suggestion of something that had already occurred.

The hearing continues.