A man already convicted of raping a Michigan teen has been found guilty in her murder, reports CBS affiliate WWMT. Prosecutors argued that 43-year-old Quinn James killed 16-year-old Mujey Dumbuya in January 2018 to stop her from testifying against him in a rape trial.

In October, after the girl's death, James was convicted on four counts of third-degree criminal sexual conduct for Dumbuya's rape and sentenced to 20 to 30 years in prison.

Mujey Dumbuya WWMT

He stood trial separately in her murder. Thursday, a jury found him guilty of first-degree premeditated murder, felony murder and conspiracy to commit first-degree murder, reports the news site MLive. He reportedly faces a mandatory sentence of life in prison without the possibility of parole.

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After the verdict was read, the teen's aunt, Janya Sannoh, thanked law enforcement and said she was glad "Mujey's case did not go cold."

"No other family no other girl needs to go through this," Sannoh said, reports WWMT. "And he's not going to hurt another girl. No other family should go through this because of him."

The student at East Kentwood High School, near Grand Rapids, disappeared Jan. 24, 2018 and was found strangled four days later in Kalamazoo. Her partially clothed body was soaked in bleach and dumped in a wooded area, the station reported.

Dumbuya had in November 2017 accused James, who at one time worked as a groundskeeper for her school district, of forcing her to have sex with him multiple times starting when she was 15, WWMT reported. James was charged with multiple counts of criminal sexual conduct and ordered to have no contact ahead of the trial with Dumbuya, who was also dating the nephew of his fiancée, according to WWMT. Dumbuya was to testify at the proceedings, scheduled to start nine weeks after her body was found, the station reports.

Prosecutors said James kidnapped her from her Grand Rapids bus stop the morning she disappeared and killed her in order to prevent her from testifying.

"He preyed on this little girl for sex and when it became a problem, he eliminated her," Kent County Assistant Prosecuting Attorney Kellee Koncki told jurors during the trial's opening statements last week, WWMT reported.

Quinn James WWMT

Dumbuya's high school guidance counselor Jennifer Twilling testified Tuesday that Dumbuya told her she was afraid of James after telling police he raped her.

"She told me on multiple occasions she knew the right thing, but she was afraid," Twilling testified Tuesday.

Twilling said Dumbuya told her James knew the location of her bus stop and she feared "something would happen to her," WWMT reported.

Prosecutors said Dumbuya's blood was found in James' rental vehicle and his DNA was found on her pants. Over six days of testimony, they reportedly laid out evidence against James including DNA, surveillance videos, wire transfers, car rental documents and witness statements. James was also heard on jailhouse calls discussing how the case against him would be over if Dumbuya "doesn't show up" to testify.

James' defense attorney, Jonathan Schildgen, said the prosecution's case was built on "theory and speculation based on the fact they think they have a powerful motive." Schildgen said James admitted to a what he said was a consensual sexual relationship with Dumbuya, but thought she was 16, not 15, MLive reported. He reportedly attacked the motive outlined by the prosecution that James killed Dumbuya in order to keep her from testifying, saying that would be "just about the dumbest plan in the history of plans."

James reportedly declined to testify in his own defense.