Boston University researchers have diagnosed former Dallas Cowboys defensive end Marshawn Kneeland with Stage 1 chronic traumatic encephalopathy (CTE) following his death in November 2025. Kneeland, who was 24, died by suicide after a high-speed police chase. His family released the findings this week to provide context regarding his struggles.
Diagnosis and Findings from the Boston University CTE Center
The Boston University CTE Center conducted a postmortem brain tissue analysis on Marshawn Kneeland after he died on November 6, 2025. Researchers confirmed the presence of Stage 1 CTE, the mildest of the disease’s four stages. While the center noted that CTE is a degenerative brain disease linked to repetitive head trauma, it emphasized that the cause of suicide is complex and that a CTE diagnosis is not definitively known to be a risk factor for self-harm.
Dr. Ann McKee, the center’s director, reported that the findings were not unexpected given the demographic of athletes she studies. McKee noted that researchers have identified the progressive brain disease in nearly half of the athletes studied who died before the age of 30. Because the disease can only be definitively diagnosed post-mortem, researchers like those at the Boston University CTE Center rely on brain donations from families to better understand how repetitive sub-concussive impacts—hits that do not necessarily result in a diagnosed concussion—contribute to the disease’s progression.
The Circumstances of Kneeland’s Death
Kneeland’s death followed a volatile sequence of events in Frisco, Texas. On the night of November 5, 2025, a Texas Department of Public Safety trooper attempted to stop Kneeland for a traffic violation after clocking him driving at speeds exceeding 145 mph. Kneeland failed to stop, leading to a pursuit that ended when he crashed his vehicle and fled on foot.
For more on this story, see Marshawn Kneeland Had Early-Stage CTE at Time of Death.
During the subsequent search, police dispatchers were alerted that individuals in a group chat with Kneeland had received messages from him indicating he might be suicidal. Officers eventually discovered his body in a portable restroom around 2:20 a.m. ET on November 6. Kneeland, who had played 18 games for the Cowboys after being drafted in the second round of the 2024 NFL Draft, started playing tackle football at age 7. His professional career began after he played at Western Michigan University.
Industry Reaction and the Persistence of CTE Risk
The diagnosis has reignited concerns regarding the efficacy of modern safety protocols in professional football. Dr. Chris Nowinski, co-founder and CEO of the Concussion & CTE Foundation, argued that the case proves that advancements in helmet technology and concussion protocols have not eliminated the underlying risk of the disease.
“Mr Kneeland played in the modern era of concussion protocols and better helmets, and yet he still developed CTE. We have no reason to believe the current generation is at a lower risk of CTE than previous generations.” — Dr. Chris Nowinski, co-founder and CEO of the Concussion & CTE Foundation
Nowinski, whose organization shared a statement from the Kneeland family via X, warned that CTE is caused by repeated head impacts rather than just concussions. Boston University’s CTE Center previously announced in 2023 that it had diagnosed CTE in 345 of 376 former NFL players studied, a rate of 91.7 percent.
Family Statement and Future Implications
Kneeland’s family, including his girlfriend, Catalina Mancera, expressed a desire to use the diagnosis to shed light on the challenges faced by athletes in high-contact sports. In their statement, they emphasized that the medical findings do not define the entirety of his life. “We continue to remember Marshawn with compassion for the person he was, rather than defining him by the final moments of his life,” the family said.
This follows our earlier report, Marshawn Kneeland Cause of Death: Dallas Cowboys Player Dies at 24.
The broader conversation around CTE continues to evolve as the NFL faces ongoing scrutiny regarding player safety. While the league has previously agreed to a $1bn settlement involving more than 5,000 former players, the diagnosis of a player who competed in the modern era underscores that the medical community remains concerned about the long-term health outcomes for current and future athletes. The case of a player who spent his youth and collegiate years in the sport highlights the cumulative nature of the damage.
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