ST. LOUIS (Reuters) - A Missouri judge is expected on Friday to release his verdict in the case of a former St. Louis police officer charged with murder in the 2011 shooting death of a black man after a car chase, according to law enforcement sources.

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Jason Stockley, 36, who is white, was arrested in May 2016 and charged with first-degree murder. He was accused of intentionally killing Anthony Lamar Smith and planting a gun in his car. Stockley testified he acted in self-defense.

Local law enforcement officials, who asked not to be named, expected Judge Timothy Wilson’s ruling sometime on Friday.

The wait has left St. Louis on edge. Officials fear a repeat of the violent protests and racial tensions that followed the 2014 fatal shooting by police of unarmed black teenager Michael Brown in Ferguson, Missouri, near St. Louis.

Activists have promised major demonstrations if Stockley is acquitted. Missouri Governor Eric Greitens on Thursday put the National Guard on standby.

U.S. police have come under heightened scrutiny after killings of numerous unarmed black people in recent years triggered widespread protests.

St. Louis Mayor Lyda Krewson said on Thursday a space for protests would be set aside near the courthouse but that violence would not be tolerated.

Smith’s fiancee, Christina Wilson, speaking at a news conference with Greitens on Thursday, appealed for a peaceful response to whatever verdict is handed down.

“If you feel like you want to speak out, speak how you feel,” Wilson said. “Just do it in a peaceful way.”

Authorities say Smith, 24, tried to flee from Stockley on Dec. 20, 2011. During a pursuit, Stockley could be heard saying on an internal police car video that he was going to kill Smith, prosecutors said.

Stockley, a passenger in the vehicle with his personal AK-47 in one hand and department-issued weapon in the other, shot at Smith’s car, St. Louis Circuit Attorney’s Office spokeswoman Susan Ryan and charging documents said. Stockley and his partner chased Smith at speeds exceeding 80 miles per hour (130 kph), the documents said.

Smith’s car began slowing when Stockley directed his partner to smash into Smith’s vehicle, court documents said. The driver slammed the police vehicle into Smith’s car and then Stockley approached the driver’s side and shot Smith five times.

The only gun recovered from the scene had only Stockley’s DNA on it, prosecutors said.

Stockley, who maintained his innocence, waived his right to a jury trial, allowing the judge to decide. He left the St. Louis Metropolitan Police Department in 2013, and additional evidence led to his arrest last year.

Smith’s family in 2013 settled a lawsuit filed against the city for $900,000, the family’s lawyer, Albert Watkins, said.