John Ferak

USA TODAY NETWORK-Wisconsin

While a federal magistrate has left the door open for Brendan Dassey to be re-tried in the death of Teresa Halbach, the loss of his confession would pose a monumental challenge for prosecutors, legal experts say.

"Without his confession being used against him, they have no case," Matt Haiduk, a suburban Chicago criminal defense attorney, told USA TODAY NETWORK-Wisconsin.

The Aug. 12 ruling by Federal Magistrate William Duffin overturned Dassey's conviction. It also scorched the prosecution's prospects of keeping Dassey in the prison system for the rest of his life. In April 2007, Dassey was found guilty of first-degree intentional homicide, sexual assault and mutilating a corpse. The trial was held in the courtroom of Manitowoc County Circuit Judge Jerome Fox.

"Dassey's confession was, as a practical matter, the entirety of the case against him on each of the three counts," Duffin wrote in his decision. "Based on its review of the record, the court acknowledges significant doubts as to the reliability of Dassey's confession."

Duffin found that the incriminating confession from Dassey, a 16-year-old special education student at the time of his arrest, had been obtained illegally, violating Dassey's constitutional rights. The magistrate ordered Dassey's release from prison in 90 days unless the Wisconsin Department of Justice decides to retry him.

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"It's not good (for the state) to get a ruling like that from a federal judge," Haiduk said. "Any rational prosecutor will take that as a sign that you need to let it go. There is also enough of an outcry, and there's going to be a huge amount of bad publicity if you retry the Brendan Dassey case when there is no corroboration of what he said and no actual evidence to convict him. It's going to be politically bad."

Complicating matters for the prosecution is the reality that two of the three trial prosecutors with a vested interest in Dassey's guilt are no longer in office.

Calumet County District Attorney Ken Kratz resigned from office after a sexting scandal and Milwaukee County Assistant District Attorney Norm Gahn has retired.

The prosecution's lone holdover is Tom Fallon. In June, Fallon was rehired as an assistant attorney general after most recently working for Dane County. In 2007, Fallon handled the closing arguments during Dassey's trial and questioned some of the witnesses.

The prosecution finished presenting its case in five days — unlike the trial of Steven Avery, which lasted several weeks.

Most of the testimony centered around Dassey's confession. The teenager's videotaped interrogation by investigators Mark Wiegert and Tom Fassbender was played for the jury during the trial.

Wiegert and Fassbender were the prosecution's star witnesses. The trial focused on Kratz's speculation that Dassey became a co-conspirator in a violent rape inside Steven Avery's trailer.

"Was he there? Absolutely. Did he help? Absolutely," Kratz told the jury in his opening statement. "Teresa Halbach got lucky. She got lucky that there was a young man who showed up. She got lucky that there was one person that could save her life. But the choices that Brendan Dassey made, the choices that he made with his uncle, ensured that instead of leaving, instead of just saying no, instead of talking uncle Steven out of it ... instead of just rescuing this girl, Brendan Dassey chose to rape this young girl, to involve himself in her murder and to help dispose of and mutilate this 25-year-old body."

Notable physical evidence was introduced during Dassey's trial:

Blood stains of Halbach in the cargo area of the Toyota RAV4 found at Avery salvage.

Ammunition shells scattered around Avery's garage.

A .22-caliber Marlin rifle kept in Avery's bedroom.

Leg cuffs and handcuffs kept in Avery's bedroom.

DNA recovered from under the RAV4 hood latch.

Small droplets of blood in the front of the RAV4..

Fallon told the jury during closing arguments that Dassey "cuts her throat right across here above the Adam's apple ... He also chooses to help carry her to the garage. He chooses to help uncuff her, to hold her down while uncle Steve ties her up. He helps carry her to the garage."

But the physical evidence incriminated Avery — not necessarily Dassey, several lawyers told the USA TODAY NETWORK-Wisconsin.

Based on the wording in his ruling, Duffin agreed.

"In closing argument, Dassey's attorney highlighted the complete absence of any DNA evidence connecting Dassey to the crimes despite extensive testing and much evidence connecting Avery to the offenses," the magistrate said. "For example, Halbach's blood was not found in Avery's bedroom as would be expected if Halbach had been stabbed and had her throat been cut there as Dassey said had happened."

One of Fallon's key prosecution witnesses was Dassey's teenage cousin Kayla Avery. But even her testimony proved to be dubious, raising further doubts about the prosecution's version of events. Kayla Avery's testimony was also singled out during the "Making a Murderer" series.

"What did Brendan tell you about the fire?" Fallon asked.

"He didn't tell me anything. I kind of made up the statement. And I'm sorry," Kayla Avery testified.

"Tell us what you said you made up?"

"That he seen body parts in there. He didn't tell me anything like that or he didn't see Teresa's body or anything like that."

"You also told the officers that Brendan told you he saw Teresa alive and pinned up, didn't you?"

"Yes."

Rob Bellin, a Neenah attorney who has followed the Halbach murder case over the years, said Duffin's decision to overturn Dassey's conviction on a federal habeas corpus appeal is a "once in a blue moon for anybody."

Such rulings are quashed in the federal system at least 99 percent of the time, Bellin said.

Bellin doubts the Department of Justice would re-try Dassey. He expects the DOJ will appeal Duffin's decision. That will buy time to perhaps strike a plea agreement with Dassey and his legal defense team led by Laura Nirider and Steven Drizin of Northwestern University's Center on Wrongful Convictions.

Bellin said the DOJ could offer to release Dassey from prison and give him credit for time served if Dassey pleads guilty to a lesser crime, such as mutilating a corpse. Now 26, Dassey has been incarcerated since he was 16. He had no prior criminal history at the time of his arrest in the Halbach murder.

Haiduk also suggested the DOJ may attempt to strike a deal that dismisses the three criminal charges, but obligates Dassey to testify against Avery if Avery wins a re-trial in his appeal.

He said the DOJ is not in a good position. DOJ officials have to take into account that there's overwhelming public support and belief in Dassey's innocence as a result of the "Making a Murderer" series, Haiduk said.

"By appealing, the prosecution would also run the risk of using it as a delay tactic. It really looks like you're trying to delay just to delay," he said. "I think the murder case against Dassey likely will be dropped but it will have some conditions that maybe he'll be available as a witness against Avery."

One of Dassey's trial lawyers, public defender Ray Edelstein of Oshkosh, told USA TODAY NETWORK-Wisconsin he expects the DOJ to appeal Duffin's ruling.

He, too, doesn't envision a retrial of his former client.

"I think the evidence is so scant," Edelstein said. "If all of the confession evidence is thrown out, how does that point to Brendan Dassey? My opinion is that the state cannot retry him without the confession."

Edelstein said Duffin's 91-page ruling "was very well-written" — probably because the judge realized the ruling would be heavily scrutinized by the federal court of appeals in Chicago.

Moreover, Duffin's ruling implied that Dassey had a solid alibi around the time Halbach may have been murdered.

"Dassey's brother testified that he was home with Dassey on Oct. 31, 2005 until about 5:20 p.m. when he left, leaving Dassey alone at home," Duffin wrote. "Dassey's brother's boss also testified that he called the Dassey residence on Oct. 31, 2005, at about 6 p.m. and spoke with Dassey."

Unfortunately for Dassey, he will likely remain incarcerated as his case remains bogged down in the appeals process, Edelstein said.

"I would not be surprised if it gets appealed and ended up with a petition for review to the U.S. Supreme Court," Edelstein said. "I totally agree with the (Duffin) decision. I just don't see how, without the confession, there's any way to retry it."

Haiduk said he studied the Dassey confession and "what the kid is saying is so far from the truth it's preposterous."

He said the DOJ's chances of getting the Seventh Circuit appeals court to overturn Duffin's ruling are slim.

"I would be shocked if any appeals court overturned the ruling," he predicted.

John Ferak of USA TODAY NETWORK-Wisconsin: 920-993-7115 or jferak@gannett.com; on Twitter @johnferak