A Cole County jury deliberated just one-hour and 10 minutes, before finding Khiry Summers guilty of second-degree murder, first-degree robbery and armed criminal action.
Summers, now 21, was convicted for his role in the April 22, 2012, robbery of marijuana that ended in the killing of Columbia drug dealer Keith Mosely, 34.
Presiding Circuit Judge Patricia Joyce will sentence Summers at a later date.
Summers faces a possible two life prison sentences - or from 10-30 years - on the murder and robbery charges, and at least three years on the armed criminal action complaint.
With the help of his attorney, Khiry Summers, now 21, turned himself in to Jefferson City police last year, nine days after Columbia drug dealer Keith Mosely, 34, was killed during a drugs-related robbery.
This morning, the Cole County jury of nine men and five women hearing his trial on murder and robbery charges will watch the video of Summers' interview with Detective Mark Edwards.
Just days after Mosely's death on April 22, 2012, a Cole County grand jury indicted Summers, Tracy Session and Brandon Chase on identical charges of second-degree murder, first-degree robbery and armed criminal action.
Prosecutors accused Chase of masterminding a robbery, to steal marijuana instead of paying for it.
During the course of that robbery, Session, now 26, fired a shot that hit Mosely in the chest, and Mosely died later at University Hospital, Columbia.
Session pleaded guilty to the charges last Nov. 7, and Presiding Circuit Judge Patricia Joyce sentenced him to 20 years in prison, which he's serving at the Southeast Correctional Center, Charleston.
A jury just 21â„2 weeks ago convicted Chase, now 30, in the case, and Circuit Judge Dan Green scheduled his sentencing for July 24.
Joyce is presiding over Summers' trial this week.
Jurors have been told Summers began with a different attorney in the case - Jefferson City lawyer Tina Crow Halcomb.
Summers' current lawyer is Boone County Public Defender David Wallis.
In his opening statement Monday afternoon, Cole County Prosecutor Mark Richardson told jurors the murder ended what had been planned as an "easy robbery," with Summers getting a gun out of his brother's car and, wearing dark clothes and a mask to hide at least part of his face, using that weapon to threaten Mosely so he would turn over the drugs.
But, when Mosely gave up the marijuana, Richardson said, Summers fired three shots into the floor to scare Mosely, before Session fired the fatal shot through the doorway.
In his opening statement, Wallis acknowledged Summers spent most of Saturday, April 21, "at his girlfriend's house on Elizabeth Street (when) he decided he needed to get some marijuana to smoke."
Wallis said Summers talked with Chase, who already had been in contact with Brent Slaughter from Columbia about getting some of the drug.
Wallis told jurors Summers was outside the apartment when he heard arguing and, fearing "for his friend's life, he took one step into the apartment and fired three times into the ground" to help save Chase.
Then both Chase and Summers than ran from the apartment "about a minute" before Session fired the fatal shot.
After the shooting, Edwards testified, Summers went back to his girlfriend's, and they drove to Illinois the next day.
One key witness was Slaughter, who told Richardson he had driven to Jefferson City after being told there were people willing to buy high-grade marijuana.
Under Wallis' cross-examination, Slaughter said he didn't remember what he had told police during separate interviews at the scene, at the hospital and, later, at the police station.
Slaughter told Richardson that, shortly after midnight, Mosely showed Chase two plastic baggies holding a total of two ounces of marijuana, and that Chase then left the apartment.
When Chase came back, Slaughter said, another black man followed him, wearing black pants, a black shirt and a mask covering the bottom half of his face.
When Summers turned himself in, Edwards said, "He was polite. ... He never refused to cooperate at any time.
"It was probably one of the best, pleasurable interviews I've had with a suspect."
But when the interview was over, Edwards said, he arrested Summers on the grand jury's indictment of the murder, robbery and armed criminal action charges.