@cyberman101,
These days, most professors use a form of plagiarism checking software. Just Google; I'm sure you'll find some.
Your pal will be caught. Tell him he's got 24 hours to either change his work or confess to your professor, or the rest of the group will go to the professor.
Then do it.
He can likely be kicked out of school for this. Don't let him take you with him.