My understanding is the messages app seamlessly transitions to using iMessage to send messages over a data connection where available. Assuming this to be the

My understanding is the messages app seamlessly transitions to using iMessage to send messages over a data connection where available. Assuming this to be the case, you wouldn't normally choose to use iMessage. It just happens if it can. If further penalty were to be considered, I expect the prosecutor would have to prove that the user intentionally took action to ensure iMessage was used for the delivery of messages instead of SMS. I suspect that would be hard to demonstrate.