Former Dallas Cowboys defensive end Marshawn Kneeland, 24, is posthumously diagnosed with Stage 1 chronic traumatic encephalopathy (CTE), according to announcements from his family and researchers. Multiple outlets report that the diagnosis follows a post-mortem analysis of his brain tissue by the Boston University CTE Center, which studies the long-term effects of repetitive brain trauma. The reports say Kneeland had early-stage CTE, classified as stage one out of four. Sources also describe that Kneeland died by suicide in November 2025. Several accounts reference that his death occurred following a high-speed police chase, though details vary by outlet in how they frame the circumstances. CBS Sports, The Oregonian, and other outlets state that the diagnosis is based on the brain-tissue review and was made public months after his death. Overall, the coverage converges on the same key points: Kneeland’s age at death, the suicide, and the researchers’ finding of early-stage CTE from a posthumous examination.