When recruits were punched and tackled during a role-playing exercise at the Texas game wardens academy last year, they were taking part in a longstanding police training tradition that critics say should be retired. At least 13 of the cadets reported injuries that day, including concussions, a torn knee and a broken wrist. Two needed surgery, and one resigned in protest. A state investigation later found nothing wrong with the drill, which its supporters say is intended to teach recruits to make good decisions under stress. The experience may have been traumatizing for some, but it was not unique. Since 2005, drills intended to teach defensive tactics at law enforcement academies have been linked to at least a dozen deaths and hundreds of injuries, some resulting in disability.