Testifying in his own defense, Hendrickson told jurors that income tax is an excise tax and excise taxes may only be levied upon those who benefit from a government privilege such as a government job. But the government called forensic accounting expert witnesses from the Internal Revenue Service who rejected Hendrickson's arguments. Hendrickson, who is free on bond to await his sentencing, was convicted in 1992 for failing to file a federal income tax return and for a conspiracy involving a fire bomb placed in a bin at a Royal Oak post office.
Source: detnews.com.
