Evidence against Weir, former Warrnambool horse trainer Jarrod McLean and stable hand Tyson Kermond, of Warrnambool, was tested in the online division of Ballarat Magistrates Court this week.

The men face charges involving corrupt betting, conspiring to deceive stewards and animal torture involving 2018 Melbourne Cup runner Red Cardinal, as well as Cup hopefuls Yogi and Tosen Basil.

Lawyers for Weir and Kermond indicated they would make applications to discharge the conspiracy charges on the basis there was "not evidence of sufficient weight to find a conviction".

On Wednesday, the court was told a Victoria Police sporting integrity intelligence unit investigation stemmed back to at least June 6, 2017.

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

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

He and McLean were arrested after uniformed and plain-clothed officers swooped on the stables in January 2019.

The court heard Weir told police during an interview that he trained "because I love horses" and "not for the punt".

During cross-examination on Wednesday, Weir's lawyer Ian Hill QC accused Detective Senior Constable Cliff Pickett of failing to provide an expert witness with the majority of video footage taken from Weir's Warrnambool stables between October 25 and November 13.

He said clinical ethologist and horse trainer Andrew McLean only viewed footage from the Warrnambool 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 were 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 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 favourable 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 horses in an attempt to replicate them on race day, including whistling and wearing 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 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.

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.

Jason Gullaci, for Mr McLean, said the covert footage did not show his client applying blinkers to the horses or holding what could have been a jigger.

During questioning, Mr Gullaci grilled the investigator about telephone transcripts attached to a hand-up brief, claiming Detective Senior Constable Pickett had "spliced and diced" parts of the conversation in order to "give it a context that is totally distorted from the transcript".

"You've taken the footy highlights of a call and you've merged them altogether," he said to the investigator.

Detective Senior Constable Pickett said he accepted he "left out some of the call" but denied "merging" the evidence.

Mr Gullaci said the police brief included a transcript of a telephone conversation between Mr McLean and another man Colin Cannon, which made reference to a "jigger".

But, he said the evidence did not include the conversation in its entirety.

Mr Gullaci said the full transcript showed Mr Cannon referring to Racing Victoria steward Dion Viella checking for microchips with a wand that would "buzz up like a jigger".

Michael Allen, for Mr Kermond, said his client was employed "under McLean" and there was no evidence of him using poly pipe or the alleged jigger on the horses in question.

Lawyers for the accused men will provide written submissions to magistrate Ronald Saines, who adjourned the finalisation of the hearing until October 8.

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