There should be a way the FBI could hack into a suspects phones and They should make multiple phones to be able to buy so like- A normal basic phone where you can get hacked easily and the FBI can read your texts, a smartphone which is a little harder for the FBI to crack and then a more expensive smartphone that the FBI can not possibly hack. So like for example, the FBI has heard that a criminal is going to meet a customer / "friend" but the FBI don't want to walk into a trap, they can simply ask the higher command if they can try and HACK the suspects phone. if they get approved they should have to go through a series of CAPTHA codes or a minigame or something else just as challenging.