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Former NFL cornerback Brandon Browner has filed an appeal of his attempted murder conviction, saying he was unfit to agree to his plea deal because he was dealing with undiagnosed bipolar disorder and post-traumatic stress disorder at the time.

TMZ Sports reported his attorneys are arguing Browner's mental health problems could be the result of CTE suffered as a result of his football career. He spent more than a decade in the NFL and CFL.

In December, Browner was sentenced to eight years in prison after pleading no-contest to attempted murder and two counts of cruelty to a child. He was arrested in July after assaulting his ex-girlfriend in front of her two children.

Browner fired his attorney after agreeing to his plea and hired Chris Darden, a former prosecutor who handled the O.J. Simpson case. Darden is expected to ask the judge to throw out the plea agreement and allow Browner to enter a new plea.

The case is set to go before a judge in March.