The Seventh Circuit Court of Appeals in Chicago met in September to consider whether Brendan Dassey, now aged 28 but was aged 16 at the time of his conviction, was properly interviewed by police or forced into confessing.
The judges were sharply divided, voting 4-3 that authorities did not cajole Dassey into admitting his crimes.
Dassey was sentenced to life in prison in 2007 after telling detectives he helped his uncle, Steven Avery, rape and kill photographer Teresa Halbach.
Dassey's conviction was overturned a year ago when a federal magistrate judge ruled that detectives took advantage of Dassey's young age and low IQ to get him to confess. In June 2017, the U.S. Seventh Circuit Court of Appeals in Chicago affirmed that August 2016 ruling by a 2-to-1 count, but the state of Wisconsin requested that seven members of that court hear the appeal. "I view this as a profound miscarriage of justice".
However, the dissenting opinion from Chief Judge Diane Wood, who was joined by judges Ilena Rovner and Ann Williams, characterizes the majority's rejection of Dassey's petition for a new trial as a "travesty of justice".
"His confession was not voluntary and his conviction should not stand, and yet an impaired teenager has been sentenced to life in prison", Rovner wrote.
It wasn't immediately clear if Dassey's attorneys would appeal to the U.S. Supreme Court.
As a result, Dassey will continue to serve out his life sentence.
Their cases gained attention in 2015 after Netflix aired "Making a Murderer", a series examining Halbach's death that spawned widespread conjecture about Avery and Dassey's innocence.
The judge pointed out in his ruling that Dassey had a low IQ, was easily coerced and changed his story multiple times, and was without proper legal representation during his police interrogations. "Today's decision is a testament to the talent of the attorneys at the Wisconsin Department of Justice who have worked tirelessly to deliver justice for the family and friends of Teresa Halbach over the last decade".