IP Addy from Google Review

Hi guys, I've offered to help out a friend who happens to own a company that has had several negative reviews on Google. It would appear that these reviews all emanate from the same person - a competitor. I've said I'd look into the possibility of tracing the review back to the individuals IP address to help him prove (or disprove) his theory of who is behind the negative reviews.

I know this can be done, however, I don't believe that it is a particularly easy task but a pointer in the right direction would be most appreciated.

Cheers,

C