OSHAWA, Ont. -- The trial of two Toronto-area brothers accused of brutally beating a black teen nearly three years ago took a surprise turn Tuesday when an officer who responded to the incident recalled details she had never previously shared with prosecutors or investigators.

Durham Regional Police Const. Barbara Zabdyr told the Oshawa, Ont., court she heard Dafonte Miller screaming when she arrived at the scene of the incident on Dec. 28, 2016.

“He was screaming that he was beaten up by the males and that they were hitting him with something,” she testified.

Her new recollection was quickly challenged by lawyers representing Michael Theriault, a Toronto police officer, and his brother Christian Theriault, who are jointly charged with aggravated assault in the incident. They are also separately charged with obstruction of justice over how they portrayed it to investigators. They have pleaded not guilty.

Prosecutors allege Michael Theriault, who was off duty at the time of the incident, and his brother chased Miller, then 19, and beat him, at times using a metal pipe.

Court has heard the Theriault brothers told investigators they caught the teen breaking into their parents' truck, and feared for their lives during the encounter.

Zabdyr testified that when she arrived at the scene in Whitby, Ont., she saw Miller face down on the driveway. He was being restrained by a white, bearded man, while another white, long-haired man stood nearby, she said.

She heard the teen scream as she approached, she said.

But defence lawyers suggested the officer's memory was tainted by the fact that she read news stories about the trial, despite a court order meant to prevent witnesses from hearing each other's evidence.

“You didn't have any such memory, did you? Until you read the newspapers,” asked Alan Gold, who represents Christian Theriault.

Zabdyr insisted the memory emerged last year in the days after she testified in a preliminary inquiry in the case.

“I've been going over this over and over and over again,” she said during cross-examination. “At the time of the preliminary, I didn't remember that part. Going over this, this is what I remember. Certain things just come to your memory.”

The officer said she did not alert the Crown or investigators that she had new information because she believed they would tell her to save it for her testimony. She said those were the instructions she received when she remembered more details before the preliminary inquiry.

Court rules dictate that prosecutors must share their evidence with the defence in order to ensure a fair trial.

Zabdyr also told the court that Michael Theriault was the one who handcuffed Miller and patted the teen down to search for hidden weapons.

When she told Miller he was under arrest for breaking into cars, “he told me that we have the wrong guy,” the officer testified. She recalled replying that “we always do,” a quip she told the court referenced the fact that all accused claim to have been wrongfully arrested.

She overheard him tell paramedics in the ambulance “that he was just walking and he got jumped and beat up,” she said. Miller was taken to hospital to be treated for his injuries.

He was charged with several offences, including assault, but the charges were later dropped.

The trial, which is taking place before a judge alone, began last week. Miller is expected to testify on Wednesday.