Over the years, I have watched several individuals being prosecuted in federal court for failure to file tax returns.  These individuals find themselves prosecuted because they have no idea what defenses are available to them.

What usually takes place is that the United States Attorney will introduce an employee of the Internal Revenue Service as a "expert witness" on the witness stand and proceed to show that the defendant had taxable income.  The proof offered to the court through witnesses is that the defendant has on file with the IRS his/her W-2 Forms.  Usually the line of questioning for the witnesses will continue for the purpose of showing the jury that the defendant relied upon personal beliefs and opinions that had no foundation in tax law.

When it comes time to present the case for the defendant, you should recall the IRS "expert witness" to the witness stand and re-affirm that IRS W-2 Forms have been filed.  You will also need to question the witness as to how a tax law is brought into effect by regulations so that you can introduce the Federal Register into evidence.

The laws of the United States cannot be implemented until the executive department adopts regulations that interpret the law and for a regulation to be adopted, it must be published in the Federal Register.  In regard to the tax laws, the Forms to be used to collect the taxes were published in the Federal Register on September 11, 1946:

Looking to page 177A-39, we find that the IRS Form W-2 is located under section 601.2(g).  Here we find that the W-2 Form may be used as an optional income tax return by employees in lieu of IRS Form 1040:

Continuing on to page 177A-41, we find the IRS Form 1040 which states that it is the Form to be used as an individual income tax return.  This Form is to be used "unless Form W-2 is filed:"

You will find these sections of the Federal Register codified at 26 USC 6011 wherein the code states:
 

6011(a)  General requirement of return, statement, or list.

(a) General rule.  When required by regulations prescribed by the Secretary any person made liable for any tax imposed by this title, or for the collection thereof, shall make a return or statement according to the forms and regulations prescribed by the Secretary.  Every person required to make a return or statement shall include therein the information required by such forms or regulations.

The term "statement" as used in 26 USC 6011(a) means the IRS W-2 Form.

You will need to locate the full text of the Federal Register so that you can introduce it into the court as evidence.  You may locate the Federal Register in a depository library of your state (usually at the state capital) or at your law library.