How the analysis was done: The 54 criminal prosecutions were identified by Bowling Green State University criminologist Philip M. Stinson and The Washington Post. Cases were culled from news reports, grand jury announcements and news releases from prosecutors. For individual cases, reporters obtained and reviewed thousands of pages of court records, police reports, grand jury indictments, witness testimony and video recordings. Dozens of prosecutors and defense attorneys in the cases were interviewed, along with legal experts, officers who were prosecuted and surviving relatives of the shooting victims.

Now, he serves as the police chief in a small community 20 miles from the scene of the shooting.

Brackney is among 54 officers charged over the past decade for fatally shooting someone while on duty, according to an analysis by The Washington Post and researchers at Bowling Green State University. This analysis, based on a wide range of public records and interviews with law enforcement, judicial and other legal experts, sought to identify for the first time every officer who faced charges­ for such shootings since 2005. These represent a small fraction of the thousands of fatal police shootings that have occurred across the country in that time.

In an overwhelming majority of the cases where an officer was charged, the person killed was unarmed. But it usually took more than that.

When prosecutors pressed charges, The Post analysis found, there were typically other factors that made the case exceptional, including: a victim shot in the back, a video recording of the incident, incriminating testimony from other officers or allegations of a coverup.

Forty-three cases involved at least one of these four factors. Nineteen cases involved at least two.

In the most recent incident, officials in North Charleston, S.C., filed a murder charge Tuesday against a white police officer, Michael T. Slager, for gunning down an apparently unarmed black man. A video recording showed Slager repeatedly shooting the man in the back as he was running away.

“To charge an officer in a fatal shooting, it takes something so egregious, so over the top that it cannot be explained in any rational way,” said Philip M. Stinson, a criminologist at Bowling Green who studies arrests of police. “It also has to be a case that prosecutors are willing to hang their reputation on.”

But even in these most extreme instances, the majority of the officers whose cases have been resolved have not been convicted, The Post analysis found.

And when they are convicted or plead guilty, they’ve tended to get little time behind bars, on average four years and sometimes only weeks. Jurors are very reluctant to punish police officers, tending to view them as guardians of order, according to prosecutors and defense lawyers.

The definition of “officers” used in the analysis extends beyond local police to all government law enforcement personnel who are armed, including sheriff’s deputies and corrections officers. The analysis included some shootings that officers described as accidental.

There is no accurate tally of all the cases­ of police shootings across the country, even deadly ones. The FBI maintains a national database of fatal shootings by officers but does not require police departments to keep it updated.