"The suspect, a former Philadelphia Police Department sergeant, has not been charged with any child porn crimes. Instead, he remains indefinitely imprisoned in Philadelphia's Federal Detention Center for refusing to unlock two drives encrypted with Apple's FileVault software in a case that once again highlights the extent to which the authorities are going to crack encrypted devices. The man is to remain jailed "until such time that he fully complies" with the decryption order."
Not sure on this specific case, and IANAL, but from reading the article it sounds as if he has been found in contempt of court. When a judge rules an individual in contempt they can sentence them to an unspecified amount of time as to make them comply. In this case, although he hasn't been charged with the "headline grabbing" crime, he is charged with contempt which has no minimum/maximum sentence and is completely up to the judge's discretion.
Believe it or not, people can be sent to jail for crimes other than child porn. For example, contempt of court is a crime punishable by imprisonment...
He's not detained without charge. He's detained on the charge of contempt of court.
"The suspect, a former Philadelphia Police Department sergeant, has not been charged with any child porn crimes. Instead, he remains indefinitely imprisoned in Philadelphia's Federal Detention Center for refusing to unlock two drives encrypted with Apple's FileVault software in a case that once again highlights the extent to which the authorities are going to crack encrypted devices. The man is to remain jailed "until such time that he fully complies" with the decryption order."