MADISON, Wis. — A federal judge in Wisconsin on Friday overturned the conviction of a man found guilty of helping his uncle kill a woman in a case profiled in the Netflix documentary series “Making a Murderer,” ruling that investigators used deceptive tactics in obtaining a confession.

U.S. Magistrate William Duffin overturned Brendan Dassey's conviction and ordered him freed within 90 days unless prosecutors decide to retry him.

Duffin said in Friday's ruling that investigators made false promises to Dassey by assuring him “he had nothing to worry about.”

“These repeated false promises, when considered in conjunction with all relevant factors, most especially Dassey's age, intellectual deficits, and the absence of a supportive adult, rendered Dassey's confession involuntary under the Fifth and Fourteenth Amendments (of the U.S. Constitution),” Duffin wrote.

Dassey confessed to helping his uncle Steven Avery carry out the rape and murder of Teresa Halbach, but attorneys argued that his constitutional rights were violated throughout the investigation.

Dassey was 16 when Halbach was killed in 2005 after she went to the Avery family auto salvage yard to photograph some vehicles.

Avery was tried and convicted separately in the homicide. Avery and Dassey are serving separate life sentences.

Dassey's case burst into the public's consciousness with the popularity of the “Making a Murderer” series that debuted in December.

Kathleen Zellner, an attorney for Avery, said in a statement that Avery was thrilled to hear of the ruling for his nephew. Avery is pursuing his own appeal.

Joe Friedberg, a defense attorney in Minnesota who was not involved in the case but is familiar with it and participated in a forum on it with Avery's first defense attorney, said he doesn't think the decision will have any bearing on Avery's case.

“The kid's confession was not entered into evidence against Avery, and I don't think it impacted Avery's trial at all,” Friedberg said.