Researchers at Boston University have diagnosed former Dallas Cowboys defensive end Marshawn Kneeland with chronic traumatic encephalopathy, a progressive brain disease linked to repeated head trauma. The diagnosis came after Kneeland’s family collaborated with the university and the Concussion & CTE Foundation to conduct a post-mortem analysis of his brain tissue.
The analysis identified Stage 1 of the disease, which is the first of four stages. Dr. Ann McKee, director of the Boston University CTE Center, stated that the findings were consistent with her expectations given Kneeland’s athletic background. She noted that the organization has identified the condition in nearly half of the athletes they have studied who died before turning 30. McKee emphasized that the research helps scientists understand the earliest stages of the disease and moves the field closer to developing diagnostic tools for living patients.
Kneeland, who played five years of college football at Western Michigan University before being drafted by the Cowboys in 2024, died by suicide in November 2025 at the age of 24. According to a report from the Texas Department of Public Safety, troopers attempted to stop his vehicle around 10:30 p.m. on the Dallas North Tollway near Keller Springs Boulevard for a traffic violation. Kneeland allegedly refused to stop, prompting a pursuit that ended when the trooper lost sight of the car.
The vehicle was later discovered abandoned after a crash near The Star in Frisco. During the subsequent search, officers were informed that Kneeland had expressed suicidal thoughts. He was found just after 1:30 a.m. with a self-inflicted gunshot wound.
Dr. Chris Nowinski, CEO of the Concussion and CTE Foundation, highlighted the significance of the diagnosis occurring in the modern era of football, which features improved helmets and concussion protocols. He clarified that these protocols do not prevent CTE, as the disease is caused by repeated head impacts rather than concussions alone. Nowinski urged the implementation of prevention protocols to reduce the number and force of head impacts at all levels of the sport.
Kneeland’s family, including his girlfriend Catalina Mancera, released the diagnosis to raise awareness about the invisible struggles faced by athletes in high-contact sports. In a statement, the family explained that the diagnosis provides context for struggles Kneeland may have faced but does not change the tragedy of his passing. They asked for privacy as they continue to grieve. Mancera gave birth to their son last month.
