Avery was jailed in 2005.
Steven Avery, the subject of Netflix’s Making A Murderer, has won a motion to appeal his murder conviction.
The new development has been hailed as a “big win” by Avery’s lawyer Kathleen Zellner, who claims that evidence in the case has been mishandled by US authorities.
Avery and his nephew Brendan Dassey were both sentenced to life in jail for killing photographer Teresa Halbach in 2005, but they have both continually protested their innocence.
The appeal, which was filed by Zellner on Avery’s behalf, is based on possible human bones found in a gravel pit.
Zellner says that they were not tested for DNA and returned to Halbach’s family – a violation of state law.
If the bones are found to belong to Ms Halbach, Zellner argues that it goes against the prosecution’s argument that she was killed at Avery’s car salvage yard in Wisconsin – where her charred remains were originally discovered a week after she went missing.
“This evidence has the potential to undo the whole case, so it is a big win,” she told Newsweek magazine.
“The case is being remanded back to the circuit court to conduct proceedings, which can include a hearing. The circuit court can grant a new trial, or if not, back to appellate court who can reverse the conviction and/or grant a new trial.”
She added on Twitter: “We are going to have an extraordinary number of constitutional violations when we are done. The [court of appeals] is letting us create an avalanche of evidence in this record. Higher courts rule.”
The huge development comes after Zellner previously argued that key new evidence could secure Avery’s release.