Death in Small Doses

One night, Nancy Lyon awakes in pain and dies shortly after--poisoned with arsenic. Her family immediately suspects her husband Richard, who left her temporarily the year before because of an affair. Nancy's brother is especially keen on getting her children away from the suspected murderer. All evidence points against Richard, but in court Richard surprisingly presents proof that his wife had depression, so perhaps she killed herself. Or is this "proof" just fake? Depicts an authentic case.