He wasn't there. He flew the coop.
"The court found, because of a lack of evidence to the contrary, that such a shotgun was not appropriate for militia use."
The U.S. Supreme Court, not having the authority to make that determination, kicked it back to the lower court for them to hear testimony. Since Miller was gone to parts unknown, they let it drop.
No decisions were made one way or the other. But since the U.S. Supreme Court asked the question, that gives us an idea what they were thinking.
Since he wasn't under indictment, he had no obligation to show up.
Since Miller was gone to parts unknown, they let it drop.
Miller was dead. His co-defendant was not, however; the government for some reason decided to offer a plea-bargain instead of going ahead with prosecution and have some creative reporting fill in the gaps.