https://www.theverge.com/2017/9/12/16298192/apple-iphone-face-id-legal-security-fifth-amendment

In the short time since Apple announced its Face ID feature for the iPhone X, we’ve seen a lot of questions about its security compared to a fingerprint or passcode. For example, if you’re arrested, can a police officer just point your phone at your face and unlock it?

Apple has some technical features that might make this harder. The iPhone X isn’t supposed to unlock if your eyes are closed, for example, and since iOS 11 reportedly lets you disable Touch ID on the fly, you might be able to do the same for Face ID. But from a legal perspective, you’re less secure unlocking a phone with your face — or just about any biometric mechanism — than with a passcode.