Marshawn Kneeland, a defensive lineman for the Dallas Cowboys, was diagnosed with stage 1 chronic traumatic encephalopathy (CTE) following his death by suicide in November 2025, according to results from a post-mortem brain tissue analysis released Tuesday by his family.
Researchers at the Boston University CTE Center identified the condition, which is the lowest level on a four-stage scale, in the 24-year-old's brain tissue. Dr. Ann McKee, director of the center, noted that finding CTE in athletes who die before age 30 has become increasingly common, stating that the disease has been found in nearly half of such studied individuals. "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," McKee said.
Kneeland, selected by the Cowboys in the 2024 NFL Draft, died from an apparent self-inflicted gunshot wound after a police pursuit. Frisco police reported that information gathered during the pursuit indicated Kneeland had expressed suicidal thoughts. His death occurred two days after he played 17 snaps in the Cowboys' loss to the Cardinals. A national crisis line is available for those experiencing suicidal thoughts or mental health crises. People can call or text 988 or chat at 988lifeline.org for free, confidential support.