When Chloe Daniels attacked a mailman out of nowhere and had other suspicious behaviors, Alexander examined her after psychiatric testing yielded no diagnoses and diagnosed her with chronic traumatic encephalopathy using an experimental technique he developed to avoid having to wait until a person has died to diagnose the condition. He was then called upon to testify at her hearing to make the case that the diagnosis should be included. He ultimately helped get her deferred prosecution.
He's a doctor and the world's leading expert on chronic traumatic encephalopathy. He developed a diagnostic test to confirm CTE during a person's life instead of waiting until death.