08/06/2017 11:39 BST | Updated 09/06/2017 12:36 BST

Kathleen Zellner, Making A Murderer Lawyer, Says Ex-Boyfriend Killed Teresa Halbach NOT Steven Avery

'Both Ms Halbach and Mr Avery have yet to receive justice.'

A lawyer acting on behalf of a man whose imprisonment was profiled in the Making a Murderer Netflix series has called for a new trial, alleging the victim may have been killed by her ex-boyfriend and not the man jailed for her death.

Kathleen Zellner, who represents Steven Avery, says his conviction was based on planted evidence and false testimony in a 1,272-page document, the first 220 pages of which are available to view on her website.

She contends Avery deserves a new trial “in the interests of justice” and because “the real controversy was never tried,” USA Today Network-Wisconsin reported.

Handout . / Reuters
Steven Avery was jailed for life over the death of Teresa Halbach in 2005 

The Wisconsin Department of Justice did not immediately respond to a request from the Associated Press for comment.

Avery, 54, was sentenced to life in prison after being convicted of first-degree intentional homicide in the 2005 death of 25-year-old photographer Teresa Halbach in Manitowoc County.

Avery’s nephew, Brendan Dassey, confessed to detectives he helped his uncle rape and kill Halbach at the Avery family’s salvage yard. A judge overturned Dassey’s conviction in August, ruling that investigators took advantage of the then-16-year-old Dassey’s cognitive disabilities and tricked him into confessing. State attorneys are appealing that decision.

Monica Schipper via Getty Images
Kathleen Zellner says Avery's conviction was based on planted evidence and false testimony 

The document filed by Zellner alleges Halbach had an “abusive” relationship with her former lover and that “jealousy was the motive.”

She also claims the ex-partner continued to have a romantic interest in Halbach which was not reciprocated and that he continued to pursue her after she began a relationship with another man.

The papers allege the ex-boyfriend “had sustained visible injuries to his hands, from fingernail scratches, around the time of her disappearance.”

Avery was sentenced to life in prison after being convicted of first-degree homicide in the 2005 death of Teresa Halbach 

Zellner adds: “Ms Halbach’s ex-boyfriend initially gave the police a false name, minimised his relationship with her, lied about crime scene evidence, controlled and led the searchers to Ms Halbach’s vehicle, had unrestricted access to the Avery property to plant evidence.”

Both Avery and Dassey maintain their innocence. The case gained national attention in 2015 after Netflix aired a documentary examining Halbach’s death. Authorities who worked on the case say the series was biased. The filmmakers have defended their work.

In Wednesday’s filing, Zellner contends that Avery’s trial attorneys failed to prove that evidence had been planted because they lacked experts and they did not conduct a thorough investigation. She also maintains that a spare key for Halbach’s sport utility vehicle found in Avery’s bedroom was planted by sheriff’s deputies. Officials involved in the case have denied any misconduct.

Handout . / Reuters
A judge turned over Brendan Dassey's conviction last year 

“Because the State did not need to establish motive, it did not spend any time trying to figure out why Ms. Halbach was murdered,” Zellner wrote. “Both Mr Avery and Ms Halbach are victims of a justice system whose success depends upon the integrity, competence and devotion of judges, law enforcement, prosecutors, and defence attorneys. Both Ms Halbach and Mr Avery have yet to receive justice.”

Dean Strang, one of Avery’s trial lawyers, said he and Avery’s other trial attorney, Jerry Buting, are glad that Zellner filed the motion and its supporting documents.

“All that really matters here, to us and we hope to everyone, is that we get closer to the truth in this case and to justice for everyone,” Strang said in an email to the AP.

In November, Zellner announced that an agreement had been signed to begin independent scientific testing on several critical pieces of evidence.

Avery and Dassey contend they were framed by law enforcement angry with Avery for filing a lawsuit against Manitowoc County over his wrongful imprisonment for a sexual assault he didn’t commit.