Indictments rare, but police do get charged over use of deadly force

FILE- This file image provided by the Los Angeles County Superior Court shows police at the scene where Oscar Grant was shot by former San Francisco Bay Area Rapid Transit police officer, Johannes Mehserle on an Oakland, Calif., train platform on New Year's Day 2009. The former transit officer was convicted of involuntary manslaughter in the shooting death of Grant. At least 400 people are killed by police officers in the United States every year, and while the circumstances of each case are different, one thing remains constant: In only a handful of instances do grand juries issue an indictment, concluding that the officer has committed a crime. (AP Photo/ Los Angeles County Superior Court, File) (The Associated Press)

FILE- This undated file image provided by the Los Angeles County Superior Court shows Oscar Grant who was shot by former San Francisco Bay Area Rapid Transit police officer, Johannes Mehserle on New Year's Day 2009. The former transit officer was convicted of involuntary manslaughter in the shooting death of Grant. At least 400 people are killed by police officers in the United States every year, and while the circumstances of each case are different, one thing remains constant: In only a handful of instances do grand juries issue an indictment, concluding that the officer has committed a crime. (AP Photo/ Los Angeles County Superior Court, File) (The Associated Press)

FILE - In this Feb. 18, 2012, file photo, Franclot Graham speaks to his son, Ramarley Graham, before a funeral services in the Bronx borough of New York. Graham was shot in his home by a police officer who mistakenly thought he had a gun. At least 400 people are killed by police officers in the United States every year, and while the circumstances of each case are different, one thing remains constant: In only a handful of instances do grand juries issue an indictment, concluding that the officer has committed a crime. (AP Photo/John Minchillo, File) (The Associated Press)

At least 400 people are killed by police in the United States every year, but even when those deaths prompt public outrage, grand juries almost always decide that the officer hasn't committed a crime.

But there are exceptions.

Successful prosecutions generally involve officers who have lied about what they've done, used excessive force to inflict punishment, or instigated confrontations for personal reasons.

Federal and state prosecutors have won convictions in several states.

This year, several officers faced criminal charges in North and South Carolina over fatal shootings.

Experts say jurors are willing to give the benefit of the doubt to officers who use deadly force on the job.

But that sympathy goes away if there is evidence that officers are using violence for retribution.