Dallas Cowboys defensive end Marshawn Kneeland was diagnosed with early-stage chronic traumatic encephalopathy at the time of his death, according to postmortem test results released Tuesday by his family through the Concussion & CTE Foundation. Kneeland died by suicide at age 24 in November.
Researchers at the Boston University CTE Center analyzed brain tissue from the 2024 second-round draft pick and determined he was in stage one of four stages of the disease. Kneeland began playing tackle football at age 7. Dr. Ann McKee, the center’s director, stated that the finding was not surprising given that the center has identified the progressive brain disease in nearly half of the athletes they have studied who died before age 30.
Kneeland’s family, including his girlfriend Catalina Mancera, issued a statement explaining that the diagnosis provides context for struggles he may have faced. They emphasized that the information is shared to help people understand the challenges NFL and other high-contact sport athletes might encounter. The family asked that Kneeland be remembered with compassion for who he was, rather than being defined by the final moments of his life.
Kneeland died on Nov. 6, 2025, following a pursuit by Frisco, Texas, police. Authorities had attempted to pull him over on Nov. 5 for a traffic violation. Dispatch audio from the incident revealed that Kneeland had sent a group text saying goodbye to his family before being found deceased with what appeared to be a self-inflicted gunshot wound.
Dr. McKee noted that the generosity of brain donor families has improved understanding of the earliest stages of CTE and is bringing researchers closer to diagnosing the condition during life. She stated that her team is dedicated to finding effective treatments and a cure for the disease.
