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Former Patriots tight end Aaron Hernandez, who committed suicide in April while serving a life sentence for murder, had chronic traumatic encephalopathy, a degenerative brain disease linked to head trauma, the New York Times reported.

Jose Baez, a lawyer for Hernandez, is announcing the development at a Thursday news conference, and Baez plans to sue the Patriots and the NFL on behalf of Hernandez's 4-year-old daughter.

Baez said researchers determined that Hernandez's case was "the most severe case they had ever seen in someone of Aaron's age." Hernandez was 27 when he was found dead in his cell on April 19.

Hernandez's brain was examined by Dr. Ann McKee, a neuropathologist who had previously conducted a study of 202 brains, 111 of them from former NFL players, and found that all but one of them was diagnosed with CTE. Of the 202 brains in the study among players from all levels of football, 87 percent had CTE.

CTE has been shown to have side effects. Several former NFL players experienced symptoms of depression and some committed suicide. It wasn't known whether Hernandez had CTE, because while a person can experience symptoms, CTE cannot be confirmed until after death.

Dave Duerson, Junior Seau, Andre Waters, Ray Easterling and Jovan Belcher preceded Hernandez as NFL players who took their own lives and were later found to have CTE.

Hernandez is among the youngest NFL players to be found with CTE, though former Giants safety Tyler Sash was also 27 when he was was found dead in September 2015. Sash also had advanced stages of the disease.

McKee, who also conducted Sash's examination, said at the time that the severity of CTE in Sash's brain was on par with the level found in the brain of Seau, who was 43 when he committed suicide.

On a severity scale of 0 to 4, Sash was a Stage 2. McKee said in a statement that Hernandez was a Stage 3.

Hernandez's suicide came five days after he was acquitted of a double slaying that took place in 2012.