Const. Ryan Simpson also told his disciplinary hearing that he never arrested Nicholas Wright, but admitted failing to inform him of his rights when he detained him for investigative purposes.
"I just absent-mindedly, forgot to advise him of that," Simpson testified.
Simpson did agree it would have been "reasonable" for Wright to believe he was in fact under arrest and admitted not telling him he was free to leave.
The officer has pleaded not guilty to making an unlawful arrest when he detained Wright, a lawyer, on Sunday June 27, 2010, the day after Black Bloc vandalism erupted in downtown Toronto.
He said he noticed Wright cycling quickly between rows of traffic and decided to stop him. He then noticed Wright had a scarf and swimming goggles around his neck, and was carrying a backpack.
Wright, 31, a lawyer, testified he gave the officer his name and address but refused to answer any further questions.
Simpson, he said, told him he was under arrest for wearing a disguise and searched him and his backpack over his objections.
"The officer said he didn't need my consent because I was under arrest," Wright testified.
"I was told I didn't have a right to remain silent because I was under arrest."
Wright said the officer was not wearing a name tag, and gave a false name when asked to identify himself.
Simpson, the first of 32 Toronto officers facing Police Service Act charges stemming from the G20 protests, denied those allegations.
Defence lawyer Alan Gold made much of the fact that Wright had goggles with him, a fact he never mentioned in either his complaint or in small-claims proceedings against the officer.
Wright agreed it was unusual to have goggles, but said other cyclists had them to protect their eyes from tear gas.
"You weren't a normal bicyclist," Gold said. "You must have intentionally omitted them ... because they looked bad for your story."
"Yes, that's correct," Wright conceded.
Gold portrayed Wright as an activist, and suggested he had turned the detention into a "badge of honour" in media interviews, a suggestion Wright called unfair.
The defence lawyer also heaped scorn on Wright's contention he had suffered minor financial losses due to the "19-minute interruption" in his life.
Testifying in his defence, Simpson said his superiors had told him to arrest anyone wearing a bandana for breach of the peace or for wearing a disguise.
Wright appeared to be leading a larger group of cyclists, who turned around when they saw the stop, the officer said.
"I had grounds to believe that he was involved in a group that was possibly becoming involved in a riotous act," Simpson said.
The officer said he handcuffed and searched Wright because he was concerned about a possible weapon, before placing him in a cruiser. A canister in the backpack turned out to contain only water.
Simpson denied threatening to arrest the cyclist for refusing to answer his questions.
Following Wright's testimony, the prosecution conceded there was no evidence against Simpson's co-accused, Const. Jason Crawford, to support charges, which were dismissed.
Retired Ontario court judge Walter Gonet will hear final arguments in Simpson's case Tuesday.