France's Zinedine Zidane, left, looks on after head butting Italy's Marco Materazzi

FILE - France's Zinedine Zidane, left, looks on after head butting Italy's Marco Materazzi in the chest as Italy's Fabio Cannavaro reacts during extra time in the final of the soccer World Cup soccer match at the Olympic Stadium in Berlin. Violence is part of the game in many sports. But when the Cleveland’s Myles Garrett ripped the helmet off Mason Rudolph and hit the Pittsburgh Steelers’ quarterback in the head with it, the Browns’ defender crossed a line _ one that attracts the attention of authorities sometimes from within their sport and in other cases from criminal prosecutors. (AP Photo/Jasper Juinen, File)