1 month of pay is probably sufficient enough to make the dude think twice about slamming someone. The goal in disciplining police officers should be the same as most criminals: corrective behavior. Punishing someone so severely they can't provide for their family for 6 months isn't corrective. Firing someone for every infraction isn't corrective. Most people can learn. Some can't. Those that show repetitive behaviors should be fired. Not sure where you draw the line, but I know when you have 700k police officers and a world with video cameras, you aren't going to achieve perfection, no matter what.

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