Ex-NFL star Brandon Browner wants his conviction overturned in his attempted murder case -- and he's playing the CTE card at the advice of his new attorney, famed O.J. Simpson prosecutor, Chris Darden.
Remember ... back in December, Browner pled no contest to attempted murder for brutalizing his ex-girlfriend in front of her two children. He was sentenced to 8 years in prison.
Browner has since fired his old lawyer and brought on Darden -- who claims the NFL star got screwed because the old attorney didn't realize Browner wasn't mentally fit to cop a plea.
In court docs obtained by TMZ Sports, Browner claims he's been diagnosed with bipolar disorder and PTSD and wasn't on his proper meds during his original hearing.
Browner also claims he can't fully concentrate or focus -- and a forensic psychologist believes this could be the result of CTE caused by the numerous hits he sustained during his 11-year NFL career.
Now, Darden and Browner are begging the judge to throw out the conviction and enter a new plea -- presumably, a not guilty plea -- so he won't spend the next 8 years behind bars.
Browner's case is set to go before a judge in March.