Andy Thompson | Appleton Post-Crescent

Alison Dirr/USA TODAY NETWORK-Wisconsin

APPLETON - New developments in the high-profile appeals of convicted killers Steven Avery and Brendan Dassey have been scarce in recent months, but that's about to change in a big way.

First up is the Dassey case. Attorneys are on the verge of filing a petition for a writ of certiorari with the U.S. Supreme Court — a legal brief asking the high court to hear his case.

In the Avery case, there is a March 30 deadline for Illinois attorney Kathleen Zellner to file an appellant’s brief with the Wisconsin Court of Appeals District 2. Zellner claims that new evidence points away from Avery as Teresa Halbach’s killer and argues that authorities planted evidence to convict him.

State prosecutors have rejected those claims, and have successfully argued that Dassey’s conviction should stand. Both men are serving life terms in Wisconsin prisons.

USA TODAY Network-Wisconsin

Dassey’s attorneys, Laura Nirider and Steven Drizin of the Center for Wrongful Convictions of Youth in Illinois, vowed in December to appeal the case to the Supreme Court after U.S. Seventh Circuit Court of Appeals reinstated Dassey’s conviction. The Supreme Court only accepts a small percentage of petitions for review.

Drizin said a high-powered legal firm has been enlisted to assist with the effort.

“ … The bottom line is that we are working on the certiorari petition with one of the most experienced Supreme Court litigation groups in the country led by an attorney who has argued before the Court dozens of times,” Drizin wrote in an email last week to USA TODAY NETWORK-Wisconsin. “We expect to file a brief within a matter of days, not weeks, and then it will be revealed who has been added to the Dassey team.”

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Drizin said Dassey’s team has recruited “some of the best and brightest lawyers” to file amicus — or friend of the court — briefs in support of Dassey’s petition.

Four of the nine Supreme Court justices must agree to accept a case to make it worthy of certiorari.

Dassey’s appeal has undergone a series of twists and turns.

On Aug. 12, 2016, U.S. Magistrate Judge William Duffin overturned Dassey’s homicide conviction, ruling that investigators made “repeated false promises” that rendered his confession to the crime involuntary. Duffin ordered that Dassey be released or re-tried, but allowed the state to appeal the ruling.

The Wisconsin Department of Justice appealed, and, on June 22, 2017, a three-judge panel at the Seventh District affirmed Duffin’s ruling by a 2-1 margin. But a few months later, the Seventh Circuit granted a request by the justice department to have the entire panel of judges rehear the case.

Last December, the federal appeals court reinstated Dassey’s conviction, ruling by a 4-3 margin that his confession wasn’t coerced. Dissenting judges called the ruling a “travesty of justice.”

While the U.S. Supreme Court takes a very limited number of cases every year, legal experts say the Dassey case might qualify because justices could provide clarity on reviewing juvenile interrogations. Dassey was 16 when he confessed

Avery’s appeal is on a different track than Dassey’s.