If the girl is below 18, your friend has committed statutory rape (which is having intercourse with a minor i.e. someone under 18). Your friend should be very worried because statutory rape is much easier to prove since it doesn't even matter that the act was consensual or that the offender did not know that the girl is below 18. Now, the big question is: why do (old) men love to sleep with children? Even former Italian PM, Sylvio Berlusconi (in his 70's), was accused of same thing. And now there's Sunderland's Adam Johnson too. One thing is certain: your friend is in a lot of trouble.