The only soldier executed for war crimes, resulting from the American Civil War, Wirz was accused - among other things - of breaking the moral law.
Questions to ponder, regarding this clip, include these:
After the trial was over, and Wirz was condemned to hang, Louis Schade - one of his lawyers - wrote a letter to then-President Andrew Johnson. Requesting clemency for his client, Schade used these - among other words - to describe what had happened during the court martial:
[T]his commission, before which the prisoner has been tried, has in many instances excluded testimony in favor of the prisoner, and, on the other hand, admitted testimony against the prisoner, both in violation of all rules of law and equity. That the whole country knows.
Every lawyer in this city and elsewhere has regarded this and the treatment the counsel suffered at the hands of the president of the commission and the judge-advocate with indignation and as an insult to the profession. My former colleagues, Messrs. Hughes, Denver, and Peck, [who had also been representing Wirz] left for that reason, and then I would have followed their example had not the prisoner had my word of honor not to forsake him. (Official Records, Series 2, Volume 8, p. 773).
As he did not grant clemency for Mary Surratt, President Johnson did not grant clemency for Henry Wirz.
This clip, from the 1970 PBS broadcast "The Andersonville Trial," features Richard Basehart (as Henry Wirz) and William Shatner (as the Army's prosecutor, Lt. Colonel Chipman).
Clip from "The Andersonville Trial," online via PBS. Copyright, Lions Gate, all rights reserved. Clip provided here as fair use for educational purposes and to acquaint new viewers with the production.