Statutory rape?

Ok so my cousin met this girl on Facebook she added him idk how she found him bc they had no mutual friends but anyways she had been coming onto him for weeks over Facebook then eventually texts her Facebook said she was 18 he even double checked and asked her and she confirmed she was 18. Anyways she was basically looking for a hook up so when my cousin had a party at his apartments he invited her she came with some friends and ended up sleeping together. Next thing you know like 2 days later my cousin is getting arrested bc the girl was only 16. She got in trouble for sneaking out that night so her parents took her phone away they saw messages between her and my 20 yr old cousin and are now pressing charges. And bc of this my cousin is facing 10 to 20 yrs and has his first court date next month. Do you think he deserves to have half of his life taken away bc he slept with someone who lied about their age. Keep in mind 16 yr olds don't look like 16 yr olds these days and you can't really check a 16 yr olds ID bc most of the time they don't have one. I must admit maybe he should've done more research but still 10 to 20 for this?!