Failure to file federal tax returns.

A friend of mine has not filed his taxes for 2000, 2001, and 2002. He has filled them out except for the Schedule C of his 1040 in 2002, for which he has insufficient business records to complete the Schedule. He refuses to file the currently completed 2000 and 2001 forms for unimportant reasons.

He has received a letter from the IRS saying that they have not received his 2001 tax return and he may face criminal prosecution if it is not sent in. They also included a form to mail with the tax return to explain why it was not filed on time. Which leads to my question... does he have to be entirely truthful in his excuse, or would a generalized white lie be a legal answer?