As Det. Const. Alec Tompras of York Regional Police pressed a robbery suspect for information on Aug. 2, 2012, a camera captured the interview from above.

"I know for a fact that you were there that day," Tompras told Gil Kim, who was being interrogated about an armed robbery of a Rogers store in Markham, Ont., north of Toronto. 

The footage of the interrogation became crucial as Kim's lawyer sought to have the charges thrown out.

In her 2017 decision, Superior Court Justice Cory Gilmore questioned why Kim was seated facing away from the camera during the interrogation. Recordings show Kim's co-accused were interviewed facing the camera.

Gilmore threw out the case against Kim, who admitted to participating in the crime, after finding that police had assaulted him and covered up their actions. 

"The only inference to be drawn" from Kim's position to the camera, Gilmore wrote, was that it was chosen "to ensure that the blood on Mr. Kim's shirt or any facial swelling would not be seen on camera."

Gilmore called Tompras's testimony about where Kim sat "disingenuous" and "bordering on ludicrous." The judge also found Tompras "fabricated" a claim about having notes to explain "how he was able to come up with precise times for events hours after they occurred."

Investigation finds dozens of other cases

Kim's case is just one example of a problem that's more prevalent than many Canadians might realize. CBC News reviewed more than 50 criminal cases over the past five years where judges found that police officers had given false or misleading testimony, and the case against the accused fell apart.

The results of the investigation are no surprise to James Lowry, a former Toronto police officer who investigated misconduct in his own police service before becoming a defence lawyer.

Lowry worries some officers may have an "end justifies the means" mentality.

"We have to do this in order to clean up the streets to help the public," he said, describing the rationale of some officers.

"That attitude has to change."