Former Dallas Cowboys defensive end Marshawn Kneeland, who died by suicide in November 2025 after a high-speed police chase, had early stage chronic traumatic encephalopathy (CTE), his family announced Tuesday.
CTE Diagnosis Confirmed
The Boston University CTE Center, which investigates long-term consequences of repetitive brain trauma, analyzed Kneeland’s brain tissue after his death. Researchers determined Kneeland, 24, was in stage one of four of CTE, a degenerative brain disease linked to repeated concussions.
CTE is known to cause violent mood swings, impulsive behavior, and depression. It can be diagnosed only after death.
Family Statement
“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, including his girlfriend Catalina Mancera, said in a statement through the Concussion and CTE Foundation. “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. One Love.”
Circumstances of Death
Kneeland shot himself after evading authorities in his vehicle and fleeing a car crash on foot. The chase began when police said Kneeland did not stop for Texas Department of Public Safety troopers over a traffic violation. Authorities lost sight of the vehicle before locating it crashed minutes later. A dispatcher told officers that people who knew Kneeland had received a group text from him “saying goodbye,” indicating he might be suicidal.
Broader Implications for Contact Sports
According to a 2021 study by Harvard Medical School and the Boston University CTE Center, NFL players are more than four times more likely to develop ALS than other men. Dr. Chris Nowinski, CEO of the Concussion + CTE Foundation, noted Kneeland’s diagnosis comes despite modern concussion protocols and better safety equipment. Kneeland started playing tackle football at age 7, played at Western Michigan University, and was selected by the Cowboys in the second round of the 2024 NFL draft.
“We have no reason to believe the current generation is at a lower risk of CTE than previous generations,” Nowinski said. “Concussion protocols do not prevent CTE, because CTE is caused by repeated head impacts, not just concussions. If we want to reduce CTE risk, we must implement CTE prevention protocols and aggressively reduce the number and strength of head impacts at every level of the game.”
If you or someone you know is in crisis, contact the National Suicide Prevention Lifeline at 988 or 988lifeline.org, or text HOME to 741741. In the UK, Samaritans can be reached at 116 123 or jo@samaritans.org. In Australia, Lifeline is 13 11 14.
