The brain damage was so severe that scientists all but gasped.

Aaron Hernandez, the former New England Patriots tight end who was convicted of murder, killed himself in prison in April at age 27. An autopsy revealed that he had brain injuries akin to those seen in afflicted former players in their 60s, researchers announced on Thursday.

The sheer extent of the damage inverts the usual question about violence and so-called chronic traumatic encephalopathy. If accumulated head trauma can cause such damage, might the injuries in turn lead to murder and suicide?

It’s a natural presumption to make, given the suicides of Junior Seau, Dave Duerson and other former football players who were found post-mortem to have C.T.E. And it’s a question that the courts will have to wrestle with.

On Friday, the National Football League vowed to defend itself against a lawsuit filed on behalf of Mr. Hernandez’s daughter and fiancée, who claims that his injuries and death were a direct result of his participation in football.