Who is liable for tax evasion, the former business owner who cooked the books or the new owner who was honest from day one?

I am considering buying a business currently owned by an acquaintance, because he is retiring from a niche industry that seems to be fairly insulated from marketplace fluctuations. I have reservations, however: I have reason to believe that my acquaintance has been cooking the books for several decades. underreporting income in order to avoid paying as much in taxes as he truly owed. Not sure there is enough of a paper trail to determine just how much he owes the IRS in back taxes (don't think he even knows). What kind of liability would we assume for his misconduct if we were to take over the business now and find ourselves audited at some point in the future?