An Edmonton police officer who stepped on a teen's head during an arrest used "inappropriate force," a disciplinary hearing found Monday.

Const. Glen Thursby was found guilty of using unlawful or unnecesary exercise of authority.

Thursby was helping RCMP at the end of a long police chase that finally ended just east of the city in the summer of 2009.

Two teens were pulled out of a stolen pickup truck with one of the boys ending up handcuffed, face down on the ground.

That's when a pair of RCMP officers say they saw Thursby go up to the boy and stomp on his head twice.

Thursby denies stomping on the teen's head, but testified at his disciplinary hearing he used his foot to keep the boy under control.

This morning, presiding officer Supt. Mark Logar, called the officer's testimony so "self-serving," he could not give it any weight. 

Logar ruled there was no reason to use any force because at that point the teen was not resisting.

The teen had just been mauled by a police dog and it makes no sense that he would resist further, risking another mauling, Logar said.

He believes Thursby stepped on the boy's head twice, using force he calls "unusual and unreasonable."

He did not find that Thursby stomped on the boy as that would have left marks, Logar said.

Thursby's sentencing hearing is scheduled for March 8th.

With files from CBC's Janice Johnston