I think Mark is looking for evidence of CTE, Chronic Traumatic Encephalopathy, which can be associated with individuals having a pattern of repeated blows to the head. It is an insidious degenerative disorder that may not manifest until decades after the trauma history. It can only currently be diagnosed post mortem.

CTE has garnered notice of late amongst football players and other athletes in contact sports. Several pro players have died due to suicide, and there was a pro wrestler who murdered his family before taking his own life.