The charge is destruction of evidence because he used a duress password (he was legitimately under duress) to wipe the encryption keys off his phone, making it impossible for officers to do anything with.
This was a violation of his 4th Amendment and 5th Amendment rights (4A is unreasonable search and siezure, while 5A is prevention of forced self-incrimination). Oh wait, the PATRIOT Act and Red Flag laws made 4A and 5A (respectively) defunct.