A forensic expert who was retained by Bryan Kohberger's defense team said his lawyers should testify in his push to walk back his guilty plea. 

Kohberger pleaded guilty last year to murdering four University of Idaho students, and he is serving four life sentences in an Idaho prison. He filed a post-conviction relief form Monday, seeking to undo his guilty plea. 

He argues the plea deal he took was the result of "false promises and blatant disinformation." He said he was coerced into taking the agreement, and his attorneys failed to communicate potentially exculpatory evidence, Fox News reported. 

The petition references hair evidence recovered during the investigation, which was found near the victims. An FBI lab, according to defense expert Brent Turvey, determined the hairs weren't from Kohberger. 

Shanon Gray, an attorney representing the family of victim Kaylee Goncalves, disputed that the evidence holds any significance. While it suggests there were other people involved, it doesn't prove Kohberger wasn't, Gray said. She also said the defense had long been aware of the evidence.