In this Friday, June 30, 2017 file photo, Shannon Kepler, left, arrives with his legal team for afternoon testimony in his third trial in Tulsa, Okla. Kepler, a former police officer who fatally shot his daughter’s black boyfriend in 2014, will face a fourth trial in the shooting death. (AP Photo/Sue Ogrocki, File)

A white former Oklahoma police officer will face a fourth trial in the shooting death of his daughter’s black boyfriend, a prosecutor said Monday.

Three mistrials in less than a year have been declared in the case of Shannon Kepler, who was charged in the August 2014 fatal shooting of 19-year-old Jeremey Lake in Tulsa.

Kepler doesn’t deny shooting Lake, but told investigators he acted in self-defense because he thought Lake was armed. Police found no weapon on Lake or at the scene.

Tulsa County District Attorney Steve Kunzweiler said in a statement Monday that prosecutors and the Tulsa Police Department “are in full agreement that this case should proceed with prosecution.”

“The very nature of our criminal justice system is premised upon the finality of a verdict,” Kunzweiler said. The prosecutor previously said jurors should be compelled to reach a verdict.

In Kepler’s most recent trial, held this month, jurors deadlocked 6-6 after almost three hours of deliberations.

All of Kepler’s previous trials have been overseen by District Judge Sharon Holmes. Juries in Kepler’s previous two trials, in November and February, deadlocked 11-1 and 10-2 in favor of guilt before Holmes declared mistrials after up to 12 hours of deliberations in each case.

It’s unclear why Holmes allowed the jury to deliberate much longer in the first two trials. A spokeswoman for Holmes on Monday said the judge would not comment on the case.

Kepler’s attorney, Richard O’Carroll, said he’s never heard of a case being tried four times and suggested there is political motivation behind the prosecution’s plan.

“It’s a waste of valuable resources,” O’Carroll said.

A spokeswoman for Lake’s family did not immediately respond to messages seeking comment about the prosecutor’s decision.

Kepler, who retired from the force after he was charged, was a 24-year police veteran who has said he was trying to protect his 18-year-old daughter, who had run away from home and was living in a crime-ridden neighborhood. O’Carroll said Lisa Kepler had been in and out of a homeless shelter after her father prohibited her from bringing men into his house.

Lake’s death is one of several in which black men have been killed by police officers. The killings have added to already tenuous race relations in Tulsa, echoing national conversations about police use of force. In Tulsa, race relations have been strained for more than a century. The city of about 400,000 has yet to fully heal from a 1921 race riot that killed 300 black residents and burned down a thriving business district.