Post-mortem brain tissue analysis revealed that former Dallas Cowboys defensive end Marshawn Kneeland had early-stage chronic traumatic encephalopathy (CTE), a degenerative brain disease linked to repetitive head trauma.
The Concussion & CTE Foundation announced the finding on Tuesday, July 7, 2026.
The Boston University CTE Center conducted the medical evaluation of the 24-year-old athlete, determining he was in stage one of the four stages of the disease.
Kneeland died by suicide in November 2025.
He was discovered by police officers inside a portable restroom in Frisco, Texas, following a high-speed police pursuit that began over a traffic violation.
Officers had clocked him driving over 145 mph.
The Concussion & CTE Foundation shared a statement from Kneeland's family, including his girlfriend Catalina Mancera, regarding the diagnosis and his football career.
"While this diagnosis does not change the tragedy of his passing, it provides important context about some of the struggles he may have been facing.
We share this information to help people understand what NFL and other high contact sport athletes might be struggling with," the family said.
The family expressed a desire to bring awareness to the condition while remembering the late defensive end for his life rather than his death.
"Raising awareness is important to us.
We continue to remember Marshawn with compassion for the person he was, rather than defining him by the final moments of his life.
One Love," the family said.
Expert Warns on CTE Prevention
Dr. Chris Nowinski, co-founder and CEO of the Concussion & CTE Foundation, commented on the diagnosis in relation to ongoing safety protocols in contact sports.
"We have no reason to believe the current generation is at a lower risk of CTE than previous generations.
Concussion protocols do not prevent CTE, because CTE is caused by repeated head impacts, not just concussions," Nowinski said.
The neuroscientist noted that the degenerative condition has been linked to numerous deaths across the NFL, hockey, and soccer leagues.
"If we want to reduce CTE risk, we must implement CTE prevention protocols and aggressively reduce the number and strength of head impacts at every level of the game," Nowinski said.
Kneeland played 18 games for the Dallas Cowboys after being selected in the second round of the 2024 NFL Draft.
He had played tackle football since age 7.
