Richard Allen's defense team rested its case Wednesday.
Allen is accused of murdering Abby Williams and Libby German on a trail in 2017.
The defense testimony lasted for several days. Witnesses included psychiatrists, forensics experts, and testimony on cam-recorder videos of Allen in prison.
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Prosecutors also included Allen's own confessions as part of their case. Jurors heard recorded phone calls from prison, in which he told his wife he killed Abby and Libby.
The defense argues Allen was having a mental breakdown and seriously ill when he began confessing to the killings while housed at the correctional facility.
Wednesday, a rebuttal witness for the prosecution testified Allen was stable around the time he confessed.
The evidence against Allen is an unspent bullet, found between the teen's bodies had been cycled through Allen's gun.
He admitted to police he was on the trail that day, but denies any involvement in the girls' murders.
The judge says both sides will receive between two and two-and-a-half hours to present their closing arguments.
Allen faces up to 130 years in prison if convicted.