"What If John Wilkes Booth Went To Trial?"

[Tom Turner]

Laurie is absolutely correct. This was also a protection against self-incrimination. The same procedure was not confined to military courts; it was also followed in civil courts with the exception of the state of Maine. So, if all the conspirators (including Booth had he survived) had been tried in a civil court they still wouldn't have been allowed to testify.

Perhaps a written statement was allowed since Azerodt couldn't be cross-examined about it and the court could simply weigh its value for what they thought it was worth. In the case of Arnold and O'Laughlen the commission apparently did make a distinction between their role in the kidnaping plot and their much less clear involvement in the murder. But Atzerodt admitted Booth had approached him to kill Lincoln (his defense being that he failed to carry out the murder), making the court a lot less likely to receive a self-serving statement in a positive manner. After all he took a room at the Kirkwood House and was hanging out their on April 14.