The attorney for Steven Avery says a voicemail inadvertently left on her phone shows the State of Wisconsin "is trying deceive" her about the location of a pelvic bone found in a gravel pit in Manitowoc County.

Kathleen Zellner sent a letter to the Wisconsin Court of Appeals and published it on

The letter states that on Feb. 8, Zellner received a packet of never-before disclosed ledger sheets that listed among the evidence a human pelvic bone. Zellner says a previous police report she received noted that human bones were separated from non-human bones and transferred to a funeral home for the family of victim Teresa Halbach.

Zellner's client, Steven Avery, is serving a life sentence for the 2005 murder of Halbach. Zellner took up Avery's appeal, which is the subject of Netflix docu-series "Making A Murderer."

Zellner says she emailed Assistant District Attorney Tom Fallon and asked him to call her immediately "to confirm whether or not the State was in possession of the human pelvic bone."

to view the Calumet County evidence reports.

Prosecuting attorney Mark Williams, intending to call Fallon, accidentally called Zellner and left this voicemail, Zellner says:

Action 2 News reached out to the law offices of Kathleen Zellner for the audio recording of the voicemail. They directed us a Rolling Stone article that contains the audio.

for the story.

Zellner says this shows that the state has misrepresented itself regarding the possession of a human pelvic bone. Zellner says the new discovery that the bone was listed as human means that "undersigned counsel does not know if prior undisclosed testing has occurred prior to the bones being returned to the Halbach family."

Zellner has filed a motion to stay Avery's appeal, claiming the state has violated law when they gave human bones found in the gravel pit over to the Halbach family.

In a police report, dated September 20, 2011, Calumet County investigators and attorneys determined what bones held as evidence could be returned to the Halbach family. Those included human bones and teeth that were collected from a burn pit on Steven Avery's property and five which Zellner says were collected from the gravel pit: Two of these are identified in the police report as "suspected human bone fragments," one as "bone fragments," and two as "possible bone fragments."

The prosecution argued tests on the gravel pit bones were inconclusive whether they were human or animal.

Zellner plans to test gravel pit bones with modern Rapid DNA technology. She believes new tests would prove those are Halbach's bones -- undermining the prosecution's case that Avery killed Teresa Halbach and destroyed her remains in a burn pit on his property, and proof, she says, that Halbach's bones in Avery's burn pit were planted.

She argues investigators broke the law by failing to preserve evidence and failing to notify Avery's attorneys of their intent to do so, violating his right to due process.

Action 2 News asked Wisconsin Attorney General Josh Kaul if he had comment on the bones and the voicemail. Kaul told us he could not comment on an ongoing investigation.