To some, Deputy Superintendent Robert E. O'Toole Jr. (search) is a cop's cop, a 36-year police veteran who commands respect from his troops. To others, he's a rogue cop with a temper.

O'Toole has become a flash point in the investigation into the death of 21-year-old Victoria Snelgrove (search), an Emerson College student killed last week by a pepper-spray pellet fired by police trying to control a crowd of 80,000 Red Sox (search) revelers.

Supporters say he is a disciplined, by-the-book cop who is well-equipped to lead the police department's Special Operations Unit. His lawyer says he did not fire the pellet that struck Snelgrove in the eye.

But O'Toole's critics say he has a tendency to use excessive force and should not have been in charge of crowd control and police deployment. They recall an incident in 1986, the last time the Red Sox played in the World Series, when a television crew filmed O'Toole slapping a drunken reveler in the face as he was being taken into custody.

"There's certainly some kind of impulse-control problem with him," said Howard Friedman, a Boston attorney who represented Rodney Armstrong, the man O'Toole slapped. "A supervisor isn't supposed to jump in and grab someone on his own, and worse is a supervisor who uses excessive force in front of all the officers he's supposed to be supervising."

Armstrong sued O'Toole and won $5,000 in punitive damages, plus $500 in compensatory damages. Friedman said the jury found that although Armstrong was not injured, O'Toole used excessive force. He was demoted, only to be reinstated years later by current police Commissioner Kathleen O'Toole, who is of no relation.

Kathleen O'Toole said she decided to give him a second chance based on his performance since the incident and the recommendations of others. "More than anybody else I appointed during my early days here, Bob O'Toole received very high marks," the commissioner said.

But she said that her longtime professional relationship with the deputy superintendent will not stand in the way of finding out what happened the night Snelgrove died.

"It's important that I emphasize that I need to be totally objective in terms of this investigation, and will go where the truth takes us. I owe that to the Snelgrove family, I owe that to Bob O'Toole, I owe that to the other officers involved," she said. "We'll leave no stone unturned. We'll find out precisely what happened that night."

Robert O'Toole's lawyer, Timothy Burke, said O'Toole fired four rounds from the compressed-air gun, but did not fire the shot that killed Snelgrove. Burke also said O'Toole believes officers were justified in firing the guns because revelers were throwing bottles at police, setting fires and swarming cars.

"It's very easy for anybody to second-guess the operations of a special unit such as this one," Burke said.