What are the penalties for claiming 2 dependents on your Earned Income Credit Unlawfully?

My Mom and Dad have been divorced since 2004 and my father is the custodial parent,and my dad is entitled to claim both of us on his Earned Income Credit. But my mother has been claiming us on her EIC since 2004 and my father got audited by the IRS in 2007 because they say he is claiming us unlawfully (When really its the opposite).The IRS says my dad owes $10,000 for claiming us when he wasn't supposed to.I don't know why they audited my dad and not my mom but I digress. All I want to know is how much trouble will my mom get in with the law if she doesn't pay the IRS all the money back she wasn't supposed to get. And how much jail time we talking here for Fraud to a government agency.