Former Dallas Cowboys defensive end Marshawn Kneeland, 24, who died by suicide in November 2025 following a high-speed police chase, is diagnosed posthumously with early-stage chronic traumatic encephalopathy (CTE). Multiple reports say his family released the results after receiving findings from postmortem analysis. According to the information shared publicly, researchers at the Boston University CTE Center reviewed Kneeland’s brain tissue and determined he had Stage 1 CTE, the earliest level in a four-stage system. The condition is described as a brain abnormality linked to repeated head impacts, which can occur in contact sports such as football. Sources also note that CTE can only be diagnosed definitively after death, based on examination of brain tissue. Several outlets frame the diagnosis as part of broader research into CTE among former NFL players, while consistently stating the key details: Kneeland’s age, the timing of his death, and the determination that the CTE was at an early stage.