Dassey and his uncle Steven Avery are serving life sentences in prison for her murder.
Back in February, attorneys filed a petition for the high court to review a federal appeals court decision which upheld Dassey's conviction.
A lower court magistrate had ruled Dassey's confession was coerced and he should be freed.
"They began by asking Petitioner's mother for permission to talk to him and by reading him his Miranda Rights," reads the state's brief. "Throughout the three-hour, noncustodial interview, investigators used only standard techniques such as adopting a sympathetic tone, encouraging honesty, and challenging his story when they believed he was lying."
It isn't known if the U.S. Supreme Court would consider his case.