Yes, Aaron Hernandez had CTE. After his death by suicide in April 2017, his brain was sent to Boston University’s Chronic Traumatic Encephalopathy Center, where researchers diagnosed him with Stage 3 CTE out of a possible 4 stages. He was 27 years old, making his case the most severe ever recorded in someone that young out of the 468 brains BU had examined at the time.
What Researchers Found in His Brain
Dr. Ann McKee, director of BU’s CTE Center, announced the findings on September 21, 2017, about five months after Hernandez’s death. The diagnosis was confirmed through characteristic buildups of a toxic protein called tau, which clumps in the brain after repeated head impacts and slowly destroys surrounding tissue.
The damage was especially concentrated in the frontal lobes, the part of the brain responsible for decision-making, judgment, and higher-level thinking. McKee’s team also found visible damage to the brain’s inner chambers, a sign of significant tissue loss. At a November 2017 press conference, McKee said that individuals with similar findings in BU’s brain bank were at least 46 years old at the time of death. Hernandez was nearly two decades younger than any comparable case.
What Stage 3 CTE Looks Like
CTE is graded on a four-stage scale, with Stage 4 being the most severe. At Stage 3, the damage is extensive enough to produce a recognizable pattern of symptoms: aggression, apathy, memory loss, difficulty with spatial awareness, and problems with executive function (the ability to plan, organize, and manage time). Stage 4 adds paranoia, language difficulties, and loss of muscle control.
CTE can only be diagnosed after death through brain autopsy. There is currently no way to detect it in a living person with certainty, which means Hernandez would not have known his diagnosis. But the behavioral profile of Stage 3 CTE overlaps significantly with the patterns people observed in him during the final years of his life.
His Football Career and Head Trauma
Hernandez played football from youth through the professional level. He was an All-American in high school, won a national championship with the University of Florida Gators in 2009, and was drafted by the New England Patriots in 2010, becoming the youngest player in the NFL at the time. He played in the Super Bowl and was one of the league’s top tight ends before his arrest.
CTE is caused by repetitive head impacts, the kind that happen on virtually every play in football, not just the hits that cause diagnosed concussions. Playing the sport from childhood through the professional ranks means years of accumulated sub-concussive blows. Tight ends, who block like linemen and run routes like receivers, absorb contact from multiple angles on nearly every snap. The total duration and intensity of Hernandez’s football career is consistent with the kind of repetitive brain trauma that produces CTE.
The Question of Violence
Hernandez was convicted in 2015 of murdering Odin Lloyd, a semi-professional football player who was dating the sister of Hernandez’s fiancée. After the CTE diagnosis became public, a question that had already been circulating took on new urgency: did the brain disease contribute to his violent behavior?
The symptoms associated with Stage 3 CTE, particularly aggression, impaired judgment, and impulsivity, align with the kind of behavioral deterioration people described seeing in Hernandez. But drawing a direct causal line between CTE and a specific criminal act is something researchers are careful not to do. Many people with CTE never commit violent crimes, and many violent criminals do not have CTE. What the diagnosis does suggest is that Hernandez’s brain was significantly compromised in exactly the regions that govern impulse control and decision-making.
Legal Aftermath
Hernandez died while his murder conviction was still on appeal. Under a Massachusetts legal principle called abatement ab initio, a court initially vacated his conviction in May 2017, essentially erasing it because he died before the appeals process finished. The state’s Supreme Judicial Court later reversed that decision and abolished the doctrine entirely, creating a new rule: when a convicted defendant dies during appeal, the conviction stands but is noted as neither affirmed nor reversed.
Separately, Hernandez’s former fiancée filed a lawsuit against the NFL and Riddell, the league’s helmet manufacturer from 1989 to 2013. The suit alleged the NFL was negligent in its concussion protocols and accused Riddell of promoting knowingly unsafe equipment through fraudulent research. Filed on behalf of the couple’s daughter, the lawsuit sought the remainder of Hernandez’s $40 million contract and claimed loss of parental consortium, arguing that the NFL’s failures contributed to the brain damage that shaped the final years of his life.
What His Case Means for CTE Research
Hernandez’s diagnosis became one of the most publicly discussed CTE cases in history, in part because of his age and in part because of the severity of his crimes. It put a spotlight on the reality that CTE is not just a disease of retired veterans in their 60s and 70s. Advanced brain degeneration can develop in players still in their 20s, particularly those who started playing football young.
His case also highlighted the limits of what CTE science can explain. A diagnosis can reveal extensive brain damage, but it cannot retroactively assign blame for specific actions. What it can do is show that a person’s brain was profoundly altered by the sport they played, in ways that affect mood, behavior, and cognition at a fundamental level.