A judge decided Thursday that a psychologist can testify about Brendan Dassey's susceptibility to giving false confessions when the teen goes on trial this month in the 2005 murder of a female photographer.
Dassey, 17, is charged with first-degree intentional homicide, mutilating a corpse and first-degree sexual assault.
Last month, a jury found his uncle, Steven Avery, 44, guilty of homicide and of being a felon in possession of a firearm in the death. He was acquitted of a mutilation charge.
Dassey was charged after he reportedly confessed to joining Avery in raping 25-year-old Teresa Halbach, killing her and burning her body near the family's auto salvage lot in Manitowoc County on Oct. 31, 2005.
Dassey later recanted his confession in a letter to the judge and refused to testify against his uncle at his trial.
Circuit Judge Jerome Fox and the prosecution viewed a three-hour recording March 26 of the expected testimony of psychologist Robert H. Gordon, who watched police video recordings of Dassey's reported confession.
Gordon is expected to testify that he feels Dassey was susceptible to making false confessions.
Law enforcement agents videotaped Dassey last year as he detailed the alleged sexual assault, murder and disposal of Halbach's body.
Dassey's attorney Mark Fremgen has said Gordon's testimony is central to his case.
Avery maintained that authorities planted evidence at the crime scene that was used against him. He said officials were angry at him after he filed a suit in relation to an 18-year prison sentence he served. DNA evidence exonerated him from rape charges related to that sentence.