Video from a Missouri courtroom shows the emotional moment a judge overturned the conviction of a man who served nearly 28 years of a life sentence for a killing he always said he did not commit.

Lamar Johnson, 50, had his eyes closed and shook his head slightly as a member of his legal team patted him on the back when Circuit Judge David Mason issued his ruling. 

"This is unbelievable," Johnson said to reporters after he was processed out at the courthouse. He thanked everyone who worked on his case, as well as the judge, but did not take any questions.

"This is an amazing day. That we showed the city of St. Louis and the state of Missouri is about justice and not defending the finality of a conviction," St. Louis Circuit Attorney Kim Gardner told KTVI. "And I would love for Mr. Lamar Johnson to spend time with his family and to live life, so thank you."

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Man in blue shirt and dark blue tie sitting with his eyes closed and lips tightened.

Lamar Johnson and his attorneys react on Tuesday, Feb. 14, 2023, after St. Louis Circuit Judge David Mason vacated his murder conviction. (Christian Gooden/St. Louis Post-Dispatch via AP, Pool)

Gardner filed a motion in August seeking Johnson’s release after an investigation her office conducted with help from the Innocence Project convinced her he was telling the truth.

Johnson was convicted of murder for the October 1994 killing of Marcus Boyd, who was shot to death on his front porch by two masked men. Police and prosecutors blamed the killing on a dispute over drug money. Johnson maintained his innocence from the outset, saying he was with his girlfriend miles away when the crime occurred.

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Lamar Johnson wearing a blue shirt hugging the Prosecutor

Lamar Johnson embraces St. Louis Prosecutor Kim Gardner on Tuesday, Feb. 14, 2023, after St. Louis Circuit Judge David Mason vacated his murder conviction. Johnson served nearly 28 years of a life sentence for a killing that he has always said he didn't commit.  (Christian Gooden/St. Louis Post-Dispatch via AP, Pool)

Johnson’s girlfriend at the time, Erika Barrow, testified that she was with Johnson that entire night, except for about a five-minute span when he left to make a drug sale. She said the distance between the friend’s home and Boyd’s home would have made it impossible for Johnson to get there and back in five minutes.

While Johnson was convicted and sentenced to life, a second suspect, Phil Campbell, pleaded guilty to a reduced charge in exchange for a seven-year prison term.

The case for Johnson’s release centered on a key witness who recanted his testimony and a prison inmate who says it was he — not Johnson — who joined Campbell in the killing.

Lamar Johnson walking out of the courtroom while receiving a pat on the shoulder.

Lamar Johnson gets a congratulatory pat on the shoulder from St. Louis Sherriif Vernon Betts on Tuesday, Feb. 14, 2023. (Christian Gooden/St. Louis Post-Dispatch via AP, Pool)

James Howard, 46, is serving a life sentence for murder and several other crimes that happened three years after Boyd was killed. He testified at the hearing that he and Campbell decided to rob Boyd, who owed one of their friends money from the sale of drugs. He also said Johnson was not there.

Howard testified that he shot Boyd in the back of the head and neck, and that Campbell shot Boyd in the side.

Woman clasping her hands together and looking upward with her lips tightened.

Erika Barrow, former girlfriend to Lamar Johnson, reacts on Tuesday, Feb. 14, 2023, after St. Louis Circuit Judge David Mason vacated his murder conviction. (Christian Gooden/St. Louis Post-Dispatch via AP, Pool)

Years ago Howard and Campbell signed affidavits admitting to the crime and claiming Johnson was not involved. Campbell has since died.

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The Republican-led state attorney general’s office fought to keep Johnson locked up. A spokeswoman for the office, Madeline Sieren, said in an email that the office will take no further action in the case. She again defended the office’s push to keep Johnson behind bars.

The Associated Press contributed to this report.