The family of former Dallas Cowboys defensive end Marshawn Kneeland has revealed that he was posthumously diagnosed with Stage 1 chronic traumatic encephalopathy, commonly known as CTE.
Brain tissue analysis conducted by the Concussion & CTE Foundation led to the diagnosis, which was confirmed by Boston University’s CTE Center. Kneeland was 24 years old when he died by suicide on November 6, 2025. Stage 1 is the least severe of the four recognized stages of CTE — a progressive brain disease that can only be confirmed through examination of brain tissue after death.
Dr. Ann McKee, who serves as director of the Boston University CTE Center and chief of neuropathology for the VA Boston Healthcare System, commented on the findings. “Unfortunately, I was not surprised to find CTE in the brain of Mr. Kneeland, because we have found this progressive brain disease in nearly half of the athletes we’ve studied who have died before the age of 30,” she said.
Dr. McKee added, “Thanks to the generosity of our brain donor families, we now better understand the earliest stages of CTE, and it is bringing us closer than ever to diagnosing it during life. My team and I are fully dedicated to finding effective treatments and a cure for CTE.”
Kneeland’s family, including his girlfriend Catalina Mancera, issued a statement on Tuesday addressing the diagnosis. “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. 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. One Love.”
Authorities say Texas police attempted to stop Kneeland’s vehicle, but he did not pull over, leading to a chase. He ultimately crashed the car, fled on foot, and was later found dead by suicide.
Kneeland was selected by the Cowboys in the second round of the 2024 NFL Draft and appeared in seven games during his rookie season. Just days before his death, on November 3, he recovered a fumble and scored the first touchdown of his career during Dallas’ 27-17 loss to the Arizona Cardinals.
