Former Dallas Cowboys defensive end Marshawn Kneeland has been diagnosed posthumously with Stage 1 chronic traumatic encephalopathy.
Kneeland’s family released the results of a brain tissue analysis performed by the Concussion & CTE Foundation. He died by suicide on Nov. 6, 2025, at the age of 24.
Boston University’s CTE Center diagnosed Kneeland at stage 1, the lowest of the four levels. CTE only can be diagnosed by studying the brain tissue of a patient who is deceased.
“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,” said Dr. Ann McKee, director of the Boston University CTE Center and chief of neuropathology for the VA Boston Healthcare System.
“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, released the following statement on 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. 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.”
According to authorities, Texas police tried to pull over Kneeland’s car and he didn’t stop, causing a police chase. He crashed the vehicle, fled on foot and later was found dead by suicide.
A second-round draft pick in 2024 by the Cowboys, Kneeland played in seven games last season. He recovered a loose ball and scored his first career touchdown in Dallas’ 27-17 loss to the Arizona Cardinals on Nov. 3.
