A Use of Force expert testified Tuesday in the trial of a Chatham-Kent OPP officer, who is charged with manslaughter. Christopher Butler said Constable Sean O’Rourke’s actions were reasonable and its “possible” his handgun could have unintentionally gone off. O’Rourke has pleaded not guilty to manslaughter in the death of Nicholas Grieves, 24, who was shot on July 7, 2021 while behind the wheel of a car along the side of Highway 401 in Chatham-Kent. Butler said police have less than half a second to draw their weapon when under threat by an armed suspect. He told the court traffic enforcement is one of the most dangerous assignments for police because they “don’t know who they’re pulling over.” Butler said – in his opinion – O’Rourke’s reaction (leaving his cruiser, walking down a slope and drawing his handgun) was reasonable given how the car was being driven. Court has previously learned Grieves was involved in a theft of $40 in gas from the Dutton ONRoute. After O’Rourke activated his emergency lights, Grieves tried to swerve around the cruiser to the right, lost control and drove down into the center median ditch, where he continued to try to get away even though the ditch was filled with water. Butler said O’Rourke was reacting to a dynamic situation that was increasingly tense. He also testified “it’s possible” O’Rourke’s handgun could have unintentionally gone off while he struggled to get out of the front seat of the car. Butler told the judge in three other cases he’s aware of, handguns have gone off while in a holster after a significant bump. On cross-examination, Butler admitted to the crown it was purely speculative and not based on any evidence at trial, that O’Rourke’s firearm could have inadvertently gone off. The Crown also noted the car was not reported stolen when O’Rourke pulled it over and he had no information on the occupants. Jason Nichol argued O’Rourke assumed based on past experiences that the drivers were suspicious. Butler countered police can’t assume that a suspect vehicle is not a threat either. The defence evidence is now concluded. Closing arguments will be held Friday and Justice Bruce Thomas said he will need time to consider his judgment.