POLICE OFTEN ARE SEEN as a thin blue line of protection between criminals and law abiding citizens, but when police use excessive force, they cross the line and become one of the criminals. Brutality incidents, evidence that police do cross that line, continue to happen all over the country, from New York City to Dayton, Ohio, to San Antonio, Texas, to Los Angeles, California.

Yet, many officers never cross the line that separates acceptable force from brutality. Many officers understand the pressures and demands of their jobs and find ways to cope with both forms of stress in a professional and acceptable manner. In some cities, entire departments have never had complaints of police brutality. Edwin Delattre points out that many officers typically react with restraint. In Character and Cops, he writes:

I have seen police officers injured because they limited their...