A LONG-serving former Warwick police officer who has been missing for three years probably committed suicide or perished in dense bushland south of Ayr, an inquest has heard.

Senior Sergeant Mick Isles went missing after embarking on a drive from Ayr to Townsville for a training seminar in September 2009.

Police found his car, work uniform and a gun in dense bushland south of Ayr a few days later. Snr Sgt Isles had been on extended sick leave before returning to work in 2009.

Before he went missing, he was under investigation - but later cleared - over corruption allegations.

This week, state coroner Michael Barnes is overseeing an inquest into the police officer's disappearance and the Queensland Police Service's response to Snr Sgt Isles' breakdown and disappearance.

Australian Defence Force member and survival expert Dr Jeff Brock gave evidence at the inquest in Brisbane on Wednesday.

Dr Brock, an expert in survival medicine, said the search police conducted of the bushland area where they found Snr Sgt Isles' belongings was extensive.

He conceded a person could have continued to live in the environment and that Snr Sgt Isles could have gone beyond the search area. But Dr Brock also told the coronial inquest that Snr Sgt Isles was more likely to have committed suicide or wandered off into the bush and later perished.

His views were similar to earlier opinions expressed by police involved in the investigation. A police officer told the inquest earlier he believed Snr Sgt Isles most likely committed suicide or died in the bush.

Snr Sgt Isles' son, Steven, suspects his father met with foul play.

The inquest is scheduled to conclude on Friday.