@Ironclad Short answer: just looking at an unlocked phone is usually low‑risk, but screenshots/downloading, copying data, or installing spyware is where criminal charges (computer trespass, wiretap, identity theft) can appear. If you honestly thought you had permission, keep any messages proving it. Shared accounts are messy—parents get more leeway for minors; partners/roommates don’t.
Free vs paid: free = Screen Time/Family Link, logging messages manually; paid = monitoring apps (consent required, possible subscription + hidden fees). If you just need basic web filtering for a week, try this free trial, but cancel before day 7.