Const. Haoyin Zheng is seen here walking out of the Edmonton courthouse on Friday. ((Janice Johnston/CBC News))

An Edmonton police officer testified on Friday that he believes there was a physical altercation between another officer and a suspect in the back seat of his cruiser.

Const. Brad Stiksma was testifying at the trial of Const. Haoyin Zheng in Edmonton provincial court.

Zheng is charged with two counts of assault and one count of assault with a weapon in the alleged beating of Lauchlin Torry, 56, and Jean-Marc Viau, 47.

Stiksma told the court he had only been on the job for approximately one year when he spotted a stolen truck and arrested the driver in the early morning hours of Dec. 15, 2008.

Two other officers were also on scene.

Stiksma testified that Zheng climbed into the back seat of his police cruiser, where one handcuffed suspect was sitting.

In his testimony, Stiksma said he walked away at that point, but then heard yelling and saw the cruiser rocking back and forth.

Stiksma said he heard the suspect yell for help, and noticed a fresh red scrape on the suspect's chin.

Sitksma testified that he was concerned about what may have happened in the back of his cruiser, but he never asked Zheng about the incident.

Hours later, Zheng was charged with assault.

In his testimony on Thursday, Torry told the court Zheng punched him in the cheek while he was being searched after he was ordered out of the truck.

Earlier in the week, Viau testified that Zheng tackled him and punched him repeatedly while he was in the back of the police car.

Zheng had been on the job for about two years when he was charged.

The trial has been delayed until December, when another police officer is scheduled to testify.