maria haberfeld, a professor of police science at the john jay college of criminal justice, in new york, blames poor police training-- not rogue cops-- for many questionable cases of lethal force. >> there are police officers who do not belong on the job, who are trigger happy. but this is not the overwhelming majority. to the contrary, this is a fraction of a fraction. but the overwhelming majority are poorly trained. >> reporter: for police officers across the country, guidelines about deadly force are based on supreme court rulings that justify it when officers feel that they or others are in imminent danger. but there are no national standards. and in the wake of so many notorious police shootings, some departments including the one here in columbus are reinforcing the idea that deadly force should be a matter of last resort. >> so, he has a knife... >> reporter: at the police academy here, veterans and rookies alike are studying videos of police involved shootings. >> what else could have been done? could this life have been saved? how would you do it yourself? is there a better wa