Nothing to Hide
If your partner is hiding any secrets in the relationship or is being unfaithful, you can find all the information that you’ll need, but may not want to find, in their phone. Asking to see your partner’s phone is a true testament to the relationship. If they say “no”, then you have a right to be concerned.
Now let’s make it clear, you should never thoroughly look through your partner’s phone. That’s a huge invasion of privacy. But it’s also comforting knowing that you can use their phone and have their passcode, in case you need to use it for whatever reason. A partner offering up their hone to you has nothing to hide.