Former Cowboys Defensive End Marshawn Kneeland Diagnosed Posthumously With Stage 1 CTE

Former Dallas Cowboys defensive end Marshawn Kneeland was posthumously diagnosed with Stage 1 chronic traumatic encephalopathy, ESPN reported. Boston University's CTE Center reached the diagnosis after Kneeland's family donated his brain for research. Kneeland died by suicide in November 2025 at age 24.

Texas police located his body early on Nov. 6 after he fled officers during a traffic stop, crashed his car and ran on foot. A Department of Public Safety report stated a trooper observed the vehicle exceeding 145 mph with multiple unsafe lane changes before losing sight of it.

Officers searching for him received reports of suicidal ideations. Kneeland's family, including girlfriend Catalina Mancera, issued a statement Tuesday. "While this diagnosis does not change the tragedy of his passing, it provides important context about some of the struggles he may have been facing," the statement said.

"We share this information to help people understand what NFL and other high contact sport athletes might be struggling with. Raising awareness is important to us. We continue to remember Marshawn with compassion for the person he was, rather than defining him by the final moments of his life.

The BU CTE Center stated that suicide is complex and multifactorial and that a post-mortem CTE diagnosis should not be considered the cause of a suicide. Records obtained by ESPN showed mental health concerns dating to 2020 at Western Michigan, including an incident in which Kneeland was required to surrender his firearm until cleared by a counselor and another in which he was found on railroad tracks expressing a desire to be struck by a train.