Mental Evaluation
After the execution, there were a handful of doctors such as Walter Channing and L. Vernon Briggs that although, never had the time to interview Czolgosz, were interested enough in the case to actually put some time into researching him and his past. They would ultimately come to the conclusion that "insanity was the most logical explanation of the crime."1 They would write that during Czolgosz's last year, he had "gone to pieces", stated by his family and would show many signs of paranoia as a mental illness. One example is that he regularly thought that people were trying to poison him so he would cook and keep to himself, not even letting anyone from his family cook for him, while speaking all the time about murder and anarchy.2
Another doctor thought that he was "weak of nature and susceptible to the teachings of Anarchists."3 It is possible that a group such as the Sila Club caught onto this, along with his sanity, and would convince him to murder the President, before they convienently disbanded, though, this is purely speculative.
The last Doctor that will be mentioned is Dr. Sanderson Christieson who listed many facts in Czolgosz's history that points toward a "distinctly abnormal condition in his character which could hardly be expected to continue much londer without a break (in his mind, so to speak) or some perculiar overt manifestiation". In this list, he said that Czolgosz was oppossed to associating with others when young, he avoided the opposite sex when older and had no close friends, he always complained of being ill and needing medicine although not appearing to need it, he would often fall asleep in chairs at any hour of the day and lastly, he quit his job at 24 apparently due to his health where he would then stay at his parents farm to spend his time doing nothing.4
An additional, but small point of interest is that after the event, former coworkers at one of the jobs he worked in the past would say that he had a "most violent temper" which some could argue, is another clue pointing toward some sort of mental illness or the former mentioned "break."5
Dispsite all the information pointing towards Czolgosz being insane, many historians today argue that he was a "committed anarchist who acted rationally" due to all the "revolutionary ferver that developed worldwide", but this absolutely negelects any mention of the research done into his life and especially interviews that were done with his family saying otherwise.6
The sanity of Czolgosz has been debated among those interested such as doctors and historians the moment he Assassinated President Mckinley and will likely continue to for many more years. Although there is not a ton of information after his arrest to work with, regarding his mental status, due to how rushed the trial was, It is clear that upon doing a good bit of research on him, Leon Czolgosz likely could not be labeled as legally sane at the time of his trial.
Footnotes
1. Dr. Walter Channing. The mental Status of Czolgosz (Brookline, Mass: American Journal of Insanity, Vol. LIX, No. 2, 1902) pp. 4
https://archive.org/details/mentalstatusczo01changoog/page/n7/mode/2up
2. Seibert, Jeffrey W., and Internet Archive. 2002. “I Done My Duty” : The Complete Story of the Assassination of President McKinley. Internet Archive. Bowie, Md. : Heritage Books. pp. 344-346 https://archive.org/details/idonemydutycompl0000seib/page/344/mode/2up?q=attention.
3. Seibert, Jeffrey W., and Internet Archive. 2002. “I Done My Duty” : The Complete Story of the Assassination of President McKinley.
4. Briggs, L. Vernon. The Manner Of Man That Kills. United States: Da Capo Press, (1983), pp. 338 https://archive.org/details/cu31924024898771/page/n317/mode/2up?q=liked+extra
5. St. Louis Post-Dispatch. “LIFE OF CZOLGOSZ THE ANARCHIST WHO SHOT PRESIDENT,” 8 Sept, 1901, Sunday Morning edition, v54n18 page 4 (col. 3 parapgraph 2). https://www.newspapers.com/image/138260734/
6. Kilar, J. The Michigan Roots of Leon Czolgosz, Fifth Estate, Spring. (1996) https://www.fifthestate.org/archive/347-spring-1996/the-michigan-roots-of-leon-czolgosz/