Brendan Dassey was found guilty Wednesday night of helping his uncle Steven Avery rape, shoot and burn Teresa Halbach in 2005.
A jury in Manitowoc deliberated four and one-half hours before convicting Dassey, 17, of all three charges against him: homicide, mutilating a corpse and sexual assault. Sentencing is set for Aug. 6.
For both sides, the case centered on a dramatic confession Dassey gave investigators. Prosecutors said it supplied the final pieces of a gruesome and mysterious puzzle.
The defense said it was all a lie, and police coerced the learning-disabled and vulnerable teen into making something up.
Ken Kratz, prosecutor, called it a tragedy which didn't have to happen. Halbach's brother Mike said his family got the verdicts it wanted.
Dassey's mother claimed the boy was set up. Mark Fremgen, attorney, said it would be up to Dassey whether to appeal.
Avery was convicted last month in the Halbach murder. He'll be sentenced June 1, and like Dassey he faces life in prison.
Avery tried to prove that Manitowoc County authorities were out to get him because he sued them for his wrongful sex conviction from 1985. He recently expressed confidence he would ultimately win his case on appeal.