A Winnipeg police officer charged with impaired driving had a second charge of refusing a breath sample dropped due to a loss of evidence, and the trial hit a snag when an out-of-town judge failed to be appointed to oversee the case.

Const. Leslie McRae, then 41 and a 10-year veteran of the force, was charged in January with impaired care and control of a vehicle, and refusing a breathalyzer. He was one of five Winnipeg police officers arrested for similar offences in 2017.

McRae intends to plead not guilty to the impaired care and control charge.

On Thursday, Brandon-based Crown Attorney Brett Rach withdrew the charge of refusing a breathalyzer. He explained to provincial court associate chief Judge John P. Guy that McRae's defence lawyer, Evan Roitenberg, would have a good case against the Crown if he pressed on for a conviction on the breath sample charge.

"That matter, I'm confident had my friend brought a loss of evidence motion it would be successful," he said.

When asked to clarify why he dropped the breathalyzer charge, Rach referred CBC News to a Manitoba Justice spokesperson.

That spokesperson has yet to clarify what lost evidence, if any, influenced Rach's decision to stay that charge.

McRae was arrested on Nov. 20, 2017. RCMP said they found him asleep in the driver's seat of a vehicle parked on the shoulder of the highway at about 8:30 a.m. and there were signs of intoxication. He was taken to the Headingley RCMP detachment for processing and refused a breath sample, according to RCMP.

The trial was ultimately postponed Thursday because Rach expected the case would be heard by an out-of-town judge but Winnipeg-based Judge Guy arrived instead.

Rach said there had been some kind of misunderstanding and asked the trial be rescheduled until a replacement was arranged.

"I thought I had communicated that I think we would be requiring an outside judge due to the fact that Mr. McRae is a Winnipeg police officer," he said.

"Ultimately the crown is going to have to eat the delay on this."

It remains unclear whether an outside judge was ever officially requested.

Guy said it was an unfortunate mistake but agreed it is reasonable in cases such as McRae's to have an outside judge.

"It's too bad because we have witnesses here, I take it," he said.

"But I think the policy is a wise one in the sense of whether the judge knows the [accused] or anything along that line, it's one that we usually have done and I am sorry through whatever miscommunication, whatever happened that that hasn't taken place so this matter could proceed appropriately today as scheduled," Guy said.

A spokesperson for Manitoba courts said there is no written policy in the province that dictates when an outside judge should be brought into a jurisdiction to hear a case. There is an assumption that all judges are capable of remaining impartial, they said.

"There may be occasions when a potential conflict is raised and when this occurs the specific circumstances will be considered on a case by case basis," the spokesperson wrote in an email.

"It's possible that a judge from the same judicial centre who has had no prior involvement with the parties could hear the matter or that a judge from a different judicial centre should. It's also possible that no reassignment is required or that bringing in a judge from another province is needed. Ultimately it comes down to the assessment of whether a reasonably informed person would remain confident that the matter is being decided fairly and this is determined by the chief Judge."

Not all cases involving police or members of the justice system charged with an offence are heard by outside judges.

Last week, Winnipeg police officer Jason Garrett, 50, had his licence taken away for one year and was fined $1,300 by Winnipeg-based provincial court Judge Kelly Moar. Garrett pleaded guilty.

This past summer, Winnipeg-based provincial court Judge Robert Heinrichs acquitted Winnipeg officer Andrew Tighe, a 23-year member of the force originally charged with impaired driving. A second charge of refusing a breathalyzer was stayed.

McRae is expected back in court next week.