By Scott Malone
BOSTON (Reuters) - Former New England Patriots player Aaron Hernandez, who killed himself in prison in April, had a "severe case" of the brain disease chronic traumatic encephalopathy, a lawyer said on Thursday as he sued the team and NFL on behalf of the athlete's young daughter.
Hernandez was a rising star in the National Football League when he was arrested in 2013 and charged with murdering an acquaintance. He was convicted of that killing but was acquitted earlier this year of gunning down two men outside a Boston nightclub in 2012. Days later, he hanged himself in a Massachusetts prison.
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His death so soon after a legal win stunned fans and his family, who asked that the brain of the 27-year-old former athlete be tested for CTE, which is linked to the sort of repeated head traumas common in football and can lead to aggression and dementia.
Researchers at Boston University, the leading center studying CTE, found pronounced signs the disease in Hernandez's brain.
"It was the most severe case they had ever seen," said attorney Jose Baez, who successfully defended Hernandez in the double-murder case this year. "It was an advanced stage."
Baez filed a lawsuit in Boston federal court against the NFL and Patriots on behalf of Hernandez's 4-year-old daughter, Avielle, citing the CTE finding and seeking unspecified financial damages for the loss of her father.
NFL spokesman Brian McCarthy said the league had not yet seen the lawsuit and could not comment. A spokesman for the Patriots did not immediately respond to requests for comment.
Boston University's CTE center on Thursday confirmed that its researchers found that Hernandez's brain showed signs of stage 3 of the disease, with stage 4 being the most severe form.
Research released by the BU CTE center this summer found signs of CTE in 99 percent of former NFL players studied.
The disease can be diagnosed only by taking brain tissue from a dead subject and has been found in athletes including Hall of Fame linebacker Junior Seau and Pro Bowl safety Dave Duerson, both of whom committed suicide.
Hernandez had a $41 million NFL contract when he was arrested at his home in June 2013 and charged with murder. He was convicted of that killing in 2015.
A judge this year vacated that conviction, because Hernandez had not exhausted all his avenues of appeal by the time he died, a move allowed by a quirk in Massachusetts law. Prosecutors are appealing.
(Reporting by Scott Malone; Editing by Bernadette Baum and Matthew Lewis)