I'm never concerned that someone will obtain data from my phone and use it against me, because I live my life lawfully and don't have any secrets on my phone that could incriminate me. However, I AM concerned that a police officer might delete my recorded conversation with him in order to destroy the record I've established against him. My experience is that some cops won't touch your phone, even if you're in jail and they have full access, while others will delete the record you created by your conversation with them if it incriminates them, and if they can.
Solution: I use an Android phone. It has both an unlock feature and the option to encrypt the phone. I think both are a good idea. There are also apps for recording that store your recording in the cloud in real time so that even if your phone is compromised, your recording won't be.