It is interesting that they are going back so far on Tucker. The IRS website says the normal statute of limitations is 3 years on a return. I wonder if this is from a previous judgement?
Statute of Limitations for Tax Refunds, IRS Audits, and Collections
3 years to claim a refund, 3 years to be audited, and 10 years to pay tax debts
“The IRS has three years to give you a refund, three years to audit your tax return, and ten years to collect any tax due. Together, these laws are called the statute of limitations. They put time limits on various tax-related actions that you and the IRS can take.”
http://taxes.about.com/od/backtaxes/qt/statute_limits.htm