The man featured in Making A Murderer was due to be released from prison in the next few weeks
Last month it was confirmed that Brendan Dassey - one of the two men convicted of murder and the focus of the Netflix docuseries Making A Murderer - was having his conviction overturned and he was to be released from prison within the next 90 days.
Federal judge William Duffin ruled on Friday that investigators had made false promises to Dassey that he "had nothing to worry about".
His ruling said the "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 US Constitution.
But now the State Of Wisconsin Attorney General's office has made the decision to fight Judge Duffin's ruling, which means that Dassey could now be prevented from being released.
The State's Attorney General Brad Schimel told Variety: "We believe the magistrate judge's decision that Brendan Dassey's confession was coerced by investigators, and that no reasonable court could have concluded otherwise, is wrong on the facts and wrong on the law.
"Two state courts carefully examined the evidence and properly concluded that Brendan Dassey's confession to sexually assaulting and murdering [photographer] Teresa Halbach with his uncle, Steven Avery, was voluntary, and the investigators did not use constitutionally impermissible tactics."