They claimed they were “American citizens,” not United States citizens. They claimed they were not subject to the federal income tax laws. They claimed paying income tax was voluntary.

Now a Lawrenceville couple has been convicted for a tax defiance scheme, the U.S. Attorney’s Office announced Tuesday.

Stephen Paul Thomas, 46, and Patricia Denese Anderson, 51, were found guilty by a federal jury of conspiring to defraud the United States and making false claims upon the Internal Revenue Service by a federal jury after a six-day trial, the news release stated.

According to the information presented in court, Thomas and Anderson, who owned a yard furnishing store and general contracting business in Duluth, conspired to avoid taxes from 1999 to 2009 and submitted false claims for refunds.

The couple stopped filing federal income tax returns in the 1990s, then hired the now-defunct American Rights Litigators to fight the IRS on their behalf, prosecutors said. ARL sold and promoted tax defiance schemes, authorities said.

“For over a decade, Stephen Thomas and Patricia Denese Anderson waged a campaign of obstruction against the IRS, culminating in filing false tax returns claiming hundreds of thousands of dollars in false refunds,” U.S. Attorney Sally Quillian Yates said in the release.

The husband and wife’s ploys to avoid taxes included sending “obstructive, frivolous and harassing documents” to the IRS and Department of Treasury and establishing business bank accounts using fake tax identification numbers to hide money, authorities said.

In 2009, the couple submitted two fraudulent tax returns claiming more than $420,000 in refunds. They also sent the government a bogus $100 billion, private registered bond to pay off their debts, prosecutors said.

They were indicted in April.

Thomas and Anderson could be sentenced to up to five years in prison on each charge and fined up to $250,0o0. They are scheduled to be sentenced in January.