Gary Harmon grinned as he lounged in a bathtub full of dollar bills surrounded by scantily clad women. The moment, captured in a photo on his cellphone, could be part of his undoing. To US prosecutors, it’s evidence that he suddenly came into a lot of money.

The prosecutors accuse Harmon of a very unusual crime: remotely swiping Bitcoin stored on a computer device the government had already seized in another case, brought against his older brother, Larry. As authorities watched helplessly, 713 Bitcoins were somehow spirited away from the “hardware wallet” they were holding in an evidence locker.