Except the smoking gun with his prints on it was stolen by the FBI from a house in another country.
The evidence should be thrown out and the case should be dismissed. There need to be consequences for the government performing an illegal search.
They could have tried to make it legal. They could have claimed it was swept up by a national security investigation, and gotten a FISA warrant, even a warrant after the fact! That would have been sneaky, and evil, but at least a better story.
As a US citizen, I see this as my government performing larceny. They either need to throw out the search, or send the FBI supervisor who authorized this to stand trial in Iceland.