Thanks for the thread from your JTR Forum on the article. Quite interesting.
Dr. E. C. Spitzka already had played a role (in 1881) in another big murder case trial. He was called for the defense as their expert on insanity in the U.S. v. Charles Guiteau, on trial for killing President Garfield. He was ignored, though most now believe Guiteau was insane. Check out Charles Rosenberg's "The Trial of the Assassin Guiteau" published in 1968.