Former Dallas Cowboys defensive end Marshawn Kneeland had early-stage chronic traumatic encephalopathy (CTE) at the time of his death, researchers at Boston University announced Tuesday. Kneeland died in March 2026 at age 27.
CTE diagnosis confirmed by brain analysis
Scientists at the BU CTE Center examined Kneeland's brain tissue after his family donated it for research. They found evidence of Stage 1 CTE, the earliest detectable form of the neurodegenerative disease linked to repetitive head trauma. The diagnosis was confirmed by Dr. Ann McKee, director of the BU CTE Center.
“Marshawn's case adds to the growing evidence that CTE can begin in young athletes, even those who played only a few seasons in the NFL,” McKee said in a statement. Kneeland played three seasons with the Cowboys after being drafted in the fourth round in 2023.
Kneeland's football career and death
Kneeland appeared in 38 games for Dallas, recording 12 sacks and 78 tackles. He missed the final eight games of the 2025 season due to a knee injury. His death was ruled accidental due to a fall at his home in Frisco, Texas, according to the Collin County medical examiner.
His family released a statement saying, “We hope that by sharing Marshawn's diagnosis, we can help other families understand the risks of football and push for safer play.”
CTE prevalence in NFL players
A 2023 study by Boston University found CTE in 345 of 376 former NFL players examined, a rate of 91.7%. Stage 1 CTE is characterized by mood swings, impulsivity, and memory lapses, though many individuals show no symptoms. Kneeland had no reported cognitive issues before his death, according to his agent.
The NFL has implemented rule changes and protocols to reduce head impacts, but critics argue more action is needed. “We offer our condolences to the Kneeland family and remain committed to advancing player safety,” the NFL said in a statement.
