(CNN) - Few police officers ever face trial for shooting deaths, let alone are convicted.
In recent years, fatal shootings of unarmed black men across the United States have sparked outrage and concerns over police use of lethal force. Despite several high-profile cases and increased video evidence, convictions have been rare.
One researcher reported that there are about 1,000 police shootings each year in the United States.
Between 2005 and April 2017, 80 officers had been arrested on murder or manslaughter charges for on-duty shootings. During that 12-year span, 35% were convicted, while the rest were pending or not convicted, according to work by Philip Stinson, an associate professor of criminal justice at Bowling Green State University in Ohio.
Here's a look at some recent police shooting cases involving African-American victims and the outcomes:
Acquitted or charges dropped
Lamar Anthony Smith
Then-St. Louis police officer Jason Stockley shot and killed Smith in December 2011, after Stockley and his partner, Brian Bianchi, witnessed a suspected drug transaction and Smith allegedly fled the scene. After the police chase ended, Stockley exited the SUV with his department-issued handgun and a personal AK-47 pistol, a violation of department policy, according to a criminal complaint. Stockley fired five times into Smith's vehicle.
Outcome: Stockley was acquitted after St. Louis Circuit Judge Timothy Wilson said the state failed to prove that Stockley did not act in self-defense.
The 23-year old man was shot after a brief chase by then-Milwaukee officer Dominique Heaggan-Brown in August 2016. The shooting after a traffic stop sparked days of unrest in Milwaukee.
Outcome: Jury found Heaggan-Brown not guilty of first-degree reckless homicide in June 2017.
The 32-year-old Minnesota man was fatally shot during a traffic stop by police officer, Jeronimo Yanez, in July 2016. Castile's girlfriend, Diamond Reynolds, live-streamed the aftermath of the confrontation and said Castile was reaching for his identification when he was shot.
Outcome: Jury found Yanez not guilty of second-degree manslaughter in the death of Castile. His family in June 2017 reached a $3 million settlement with the city of St. Anthony, Minnesota. St. Anthony and the city of Roseville settled with Reynolds in November 2017 for $800,000.
The 40-year-old man was shot in September 2016 by Tulsa Police Officer Betty Shelby after Crutcher's SUV was found stalled in the middle of the street. Shelby testified that she opened fire because she feared for her life. Videos of the shooting showed Crutcher walking on the road with his arms in the air before being shot.
Outcome: Jury found Shelby not guilty of felony manslaughter in May 2017.
The 25-year-old man was arrested by Baltimore Police after he was found with a knife in his pocket in April 2015. Gray died after suffering a neck injury while in police custody. A Baltimore grand jury indicted six police officers on a range of charges from involuntary manslaughter to reckless endangerment.
Outcome: Three were found not guilty, three officers had their charges dropped. Baltimore officials in September 2015 approved a $6.4 million settlement with Gray's family for all civil claims tied to his death.
The 43-year-old who was pulled over for a missing front license plate was shot in the head in a July 2015 incident captured on body-camera video. The officer, Ray Tensing, was charged with murder and voluntary manslaughter. Tensing testified that he was being dragged by the left arm when he reached up and shot DuBose, while prosecutors said he wasn't being pulled by the car and didn't need to fire at DuBose.
Outcome: A mistrial was declared in 2016. A second mistrial was declared in 2017 after juries deadlocked over a verdict.
The 50-year-old man driving with a broken brake light was shot while running away from North Charleston police officer, Michael Slager. Slager was charged with first-degree murder after a cell-phone video of the April 2015 incident was released. He pleaded guilty in May 2017 to the federal charge of violation of civil rights by acting under the color of law.
Outcome: Slager's 2016 state murder trial ended in a mistrial. US District Court Judge David Norton ruled in 2017 that the underlying offense to a civil rights charge was second-degree murder and sentenced Slager to 20 years in federal prison.
The 28-year-old man was fatally shot in a New York housing project. Police officer Peter Liang, who had been on the job 18 months, was on patrol in the dark stairwell of a Brooklyn housing project in November 2014 when he fired his gun. He testified that it was an accidental discharge. The bullet ricocheted off a wall and struck Gurley in the chest.
Outcome: Liang was found guilty of second-degree manslaughter and official misconduct. A State Supreme Court justice in Brooklyn reportedly spared Liang jail time, ordering him to serve five years probation, 800 hours of community service and three years probation. The justice, Danny Chun, also reduced Liang's second-degree manslaughter charge to criminally negligent homicide, ruling Liang failed to perceive the risk that his actions would lead to Gurley's death.
Supporters said that Liang, a Chinese-American, was singled out for prosecution.
Eric Courtney Harris
The 44-year-old man was shot in Tulsa, Oklahoma, by Robert Bates, a volunteer reserve sheriff's deputy for the county sheriff's office in April 2015. Officers were conducting a sting operation to try to catch Harris illegally selling a gun and had pursued, then tackled him when Bates fired his pistol into Harris' back. Bates, 74, said he had meant to use his Taser, not his revolver.
Outcome: Bates was found guilty of second-degree manslaughter. He was sentenced in June 2016 to four years in prison, with credit for time served; he was released in October 2017, court documents show.
The 43-year-old man died after being tackled to the ground and held in a chokehold by New York City police officers on July 17, 2014, for allegedly selling cigarettes illegally. Garner, who has asthma, said, "I can't breathe," as the incident was captured on cell-phone video and died later that day.
Outcome: Grand jury decided not to indict Officer Daniel Pantaleo. The city settled with Garner's estate for $5.9 million.
The unarmed 18-year-old was fatally shot after a struggle with a police officer in Ferguson, Missouri, on August 9, 2014. Documents show that Officer Darren Wilson fired his gun 12 times.
Outcome: Grand jury decided not to indict Wilson, leading to renewed protests. Brown's family reached a civil settlement with the city in June 2017.
The 12-year-old Cleveland teenager was shot by a police officer, who was responding to a 911 call claiming a person was pointing "a pistol" at people. An officer in training, Timothy Loehmann, shot at Rice, who was carrying an air pistol, within moments of arriving at the scene in November 2014.
Outcome: A grand jury decided not to indict Loehmann or the officer who was with him, Frank Garmback. Loehmann was fired in May 2017 for being untruthful on his job application, and Garmback was suspended for 10 days for violating tactical rules relating to how he drove to the shooting scene. A dispatcher was suspended for eight days in March 2017 for failing to relay a citizen's 911 report that Rice was "probably a juvenile" and that his gun was "probably fake," and another officer was suspended for two days at that time for working a second job near the shooting scene without permission.
The 28-year-old woman was found dead in her cell three days after being arrested in Waller County, Texas, for allegedly failing to use her turn signal in July 2015.
Outcome: Grand jury decided not to indict any of the county jail employees.
The 37-year-old Louisiana man was fatally shot after being pinned to the ground by officers outside a Baton Rouge convenience store in July 2016. Police said he was reaching for a gun.
Outcome: No federal civil rights charges were filed against the officers, but state charges are possible. The Louisiana State Police, with a prosecutor from the state Justice Department, launched an investigation in May 2017.
Cases that have yet to go trial
The 17-year-old Chicago teenager died after being shot by a police officer 16 times in October 2014. Dashcam video of the shooting contradicted nearly everything police said happened the night he died in October. It showed McDonald walking away from police as he held a 4-inch knife, not lunging toward officers, as police had said. The officer, Jason Van Dyke, was charged with first-degree murder and in 2017 indicted on 16 additional counts of aggravated battery with a firearm. He has pleaded not guilty. Three other officers were charged in June 2017 with conspiracy, official misconduct and obstruction of justice, a special prosecutor said.
The 15-year-old teenager was fatally shot by a Texas police officer as he was riding in a car while leaving a house party on April 29, 2017. Police in Balch Springs said the officer fired into a car as it was driving away from a party, killing Jordan, an unarmed black teenager in the front passenger seat. That officer, Roy Oliver, was fired on May 2, 2017, and prosecutors charged him with first-degree murder three days later. A grand jury indicted Oliver two months later on one count of murder in Edwards' death and four counts of aggravated assault with a deadly weapon by a public servant in connection with the four other people in the car. His jury trial is set to begin January 22, 2018.