"iPhones encrypt user data by default. Those in physical possession normally cannot access the phone’s data, such as contact list, saved messages, or photos, without first unlocking the phone with a passcode or fingerprint. Malwarebytes’ post says GrayKey can unlock an iPhone in around two hours, or three days or longer for 6 digit passcodes."
https://motherboard.vice.com/en_us/article/vbxxxd/unlock-iphone-ios11-graykey-grayshift-police
https://motherboard.vice.com/en_us/article/vbxxxd/unlock-iphone-ios11-graykey-grayshift-police