Before Aaron Hernandez committed suicide in in jail last April, his brain had already begun to deteriorate significantly — a result of severe chronic traumatic encephalopathy (CTE), a degenerative brain disease that has been linked to head trauma.
According to a statement from Boston University’s CTE Center, the 27-year-old former football player “had early brain atrophy and large perforations in the septum pellucidum, a central membrane.”
In other words, his brain had started to shrink and there were holes in the membrane that divides the two cerebral hemispheres.
Boston University determined that Hernandez’s Stage 3 CTE was unusually severe for a 27-year-old. “CTE is associated with aggressiveness, explosiveness, impulsivity, depression, memory loss and other cognitive changes,” the University said in the statement.
“Aaron Hernandez’s advanced stage 3 of CTE is normally found in the median age of a 67-year-old man,” Hernandez family attorney Jose Baez tells PEOPLE.
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The family, on behalf of Hernandez’s 4-year old daughter, Avielle Janelle Hernandez, is suing the NFL and the New England Patriots in connection with Hernandez’s death. “It’s a loss of consortium claim,” says Baez. “She’s growing up without a father because of the negligence of the NFL.”
Hernandez’s family believes his CTE contributed to some of his behavior. He hanged himself with a bed sheet just five days after he was acquitted of double murder charges in the deaths of two men outside a Boston nightclub in 2012. He was still serving a life sentence for the 2013 murder of Odin Lloyd, his fiancée’s sister’s boyfriend. He was not eligible for parole.
(With Hernandez’s death, his conviction for Lloyd’s murder was voided because of a little-known legal doctrine in Massachusetts that vacates convictions if a defendant dies before their direct appeal is complete.)
“While we still maintain that he was innocent [of the murders], the CTE can explain a lot of his behavior,” Baez says. “The impulsiveness can be a symptom of CTE. We think that the CTE explains a lot of things that Aaron did, including his supposed suicide.”
CTE cannot be diagnosed in living subjects; it is only found during autopsies. Several former NFL players, including Junior Seau, were diagnosed with the disease after committing suicide.
In July, Boston University researchers published a study in the Journal of the American Medical Association that claimed that CTE was detected in 99 percent of brains obtained from National Football League players. Some have cautioned that the findings might have a selection bias because the brains were submitted by family members of players who showed possible symptoms of the disease.
Neither the NFL or the New England Patriots have returned PEOPLE’s calls for comment.