Miller didn’t even show up and defend himself.
It is much, much worse than Miller not showing up.
The entire case was created by Judge Heartsill Ragon. He was the Chuck Schumer of his time, extremely hostile to the idea of an armed citizenry, and the Second Amendment.
Miller was just his instrument to create the best possible test case for the NFA of 1934.
No opposition to the case was presented. The defense attorney was appointed by Heartsill Ragon.
Ragon had been appointed to the bench by FDR, a few years earlier, and was a major proponent of the New Deal when he was a member of Congress.