It was one of the most daring and risky legal maneuvers in last week's post-conviction filing by Steven Avery's criminal defense lawyer Kathleen Zellner.

Zellner declared in documents filed at the Manitowoc County Courthouse that she suspects Teresa Halbach's killer was her on-again, off-again boyfriend, Ryan Hillegas.

Their relationship lasted roughly five years, beginning in high school, in the small farming community of Hilbert. Halbach, 25, vanished on Halloween 2005. Manitowoc County Sheriff's officials immediately targeted Steven Avery, a previously exonerated man, who lived in a red trailer on his family's salvage yard.

Zellner's motion for a new trial included sworn affidavits in her 1,250-page post-conviction filing from 10 law enforcement, legal profession, medical and scientific experts. She hopes it will lead a judge to order a new trial for Avery, who is the subject of the Netflix docu-series Making a Murderer.

It was one of the most daring and risky legal maneuvers in last week's post-conviction filing by Steven Avery's criminal defense lawyer Kathleen Zellner.

Identifying Hillegas as the suspect isn't sitting well with those who are convinced Avery killed Halbach and belongs in prison for life.

"It's alarming that in the face of such overwhelming evidence of Mr. Avery's guilt, Ms. Zellner, who has devoted her career to righting wrongful convictions, has so recklessly accused the victim's former boyfriend without a shred of legitimate evidence backing her claim and with no regard for the harm she has caused," said Michael Griesbach, an assistant district attorney in Manitowoc who has authored multiple books about Avery.

Griesbach emphasized he was speaking with USA TODAY NETWORK in his capacity as a published author, not as a Wisconsin district attorney.

Zellner said her legal team attempted to interview Hillegas, who lives in the Milwaukee area, over the past 18 months, but had no success.

"Our investigators contacted Mr. Hillegas to interview him," Zellner told USA TODAY NETWORK. "He was told that we wanted to rule him out as a potential suspect, but we needed answers to certain questions related to his alibi, abusive relationship with Teresa Halbach, knowledge of her password, injuries to his left hand, interaction with law enforcement from Nov. 3 (2005) onward, damage to Teresa Halbach's parking light, access to Avery property Nov. 7. Mr. Hillegas never responded."

A message seeking comment was left on Hillegas cell phone Monday, but he did not immediately respond.

Here are the key points in Zellner's motion relating to Hillegas as a suspect: