Former Dallas Cowboys defensive end Marshawn Kneeland had early stage chronic traumatic encephalopathy (CTE) at the time of his death in November 2025, his family announced Tuesday. The Boston University CTE Center analyzed Kneeland's brain tissue after his passing and determined he was in stage one of four of the degenerative brain disease.
CTE is linked to repeated head trauma and can cause symptoms such as mood swings, impulsive behavior, and depression. It can only be diagnosed posthumously. Kneeland was 24 at the time of his death.
"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," Kneeland's family said in a statement issued through the Concussion and CTE Foundation. "We share this information to help people understand what NFL and other high contact sport athletes might be struggling with."
Kneeland died by suicide after a high-speed chase with police. Authorities attempted to stop him for a traffic violation, but he fled, eventually crashing his vehicle. As officers searched for him after he fled the crash site on foot, a dispatcher indicated that Kneeland had sent a group text saying goodbye, suggesting he might be suicidal.
Kneeland began playing tackle football at age 7 and played collegiately at Western Michigan University before being selected by the Cowboys in the second round of the 2024 NFL draft. The diagnosis comes despite modern concussion protocols and safety equipment in professional sports.
Dr. Chris Nowinski, CEO of the Concussion & CTE Foundation, stated that current concussion protocols do not prevent CTE, as the disease is caused by repeated head impacts, not solely concussions. He emphasized the need for CTE prevention protocols and a reduction in the frequency and intensity of head impacts across all levels of the sport to lower the risk of CTE.