Minor readily admitted to shooting Merrett. He produced the gun, and a Bowie knife as well, which was concealed behind his back. His trial was in April, but during his imprisonment in London it became obvious that Minor had issues. He kept telling Scotland Yard that the Fenian Brotherhood (a radical Irish organization) was coming to his jail cell at night and trying to poison him. Apparently they slipped through the windows and hid in the rafters of the roof. There were also the sexual obsessions.
Minor kept alternating between the Irish trying to do him in, or submitting him to terrible, sexual predations. The result of the trial, complete with a landlady's testimony about the imaginary Irish and the constant parade of whores to his rooms (or he to theirs), was that Dr. William C. Minor, a retired Captain in the U. S. Army, was to be formally designated in Britain by Broadmoor File Number 742, and held in permanent custody as a "certified criminal lunatic."
He was going to spend the rest of his life labelled a lunatic.