An Edmonton police officer with an otherwise perfect record has been docked 10 hours pay at a disciplinary hearing for a mistake he made more than three years ago.

In December 2009 Const. Ken Smith was working at a northside checkstop.

When a taxi filled with passengers passed by, Smith heard someone yell a profanity at him.

The officer got in his cruiser, pulled the taxi over and told the front seat passenger to get out.

But he made the mistake of not spelling out why, so everything after that became an unlawful or unnecessary exercise of authority.

Smith pulled the man out of the cab and took him to the ground, pepper spraying him in the face.

At a disciplinary hearing Friday, Smith was docked 10 hours without pay, worth $460.

The presiding officer noted Smith's many letters of commendation and otherwise spotless record.

Supt. Mark Logar described Smith as "one of the more thoughtful and informed members of the service."

He thinks Smith has learned his lesson, but he wants the public and the rest of the police service to know it's essential to follow procedure.

"When you do any type of enforcement, do it properly," said Logar. "That's the message that needs to be sent out here."

With files from CBC's Janice Johnston