It's extremely hard to convict officers accused of serious crimes.
Since 2005, 70 officers in this country have faced charges related to an on-duty shooting.
Only 23 were found guilty.
The outrage pointed at the acquittal of Baltimore police officer Edward Nero in the death of Freddie Gray further emphasizes this point.
It's also something seen in other cases around the nation, like in Cleveland after a grand jury didn't indict the officer who shot 12-year-old Tamir Rice.
Researchers at Bowling Green University said about 1,100 people are killed in police shootings every year.
But in 2015, just 18 officers were charged and only three were convicted.
