(CNN) -- A self-described white supremacist charged with plotting to kill President-elect Obama claims in court filings that his indictment should be thrown out because there were too many African-Americans on the grand jury.
Paul Schlesselman, left, and Daniel Cowart are accused of planning to kill more than 100 African-Americans.
Daniel Cowart, 20, of Bells, Tennessee, was indicted earlier this month on charges of illegally possessing a sawed-off shotgun, conspiracy to rob a federally licensed gun dealer and making threats against a presidential candidate.
Prosecutors allege Cowart and Paul Schlesselman, 18, of West Helena, Arkansas, plotted a "killing spree" against African-Americans and hoped to cap their rampage by assassinating Obama, then the Democratic presidential candidate, days before the election.
The two planned to dress in white tuxedos as they carried out the assassination, prosecutors said.
Both Cowart and Schlesselman appeared before a U.S. magistrate judge in Memphis, Tennessee, on November 6 and pleaded not guilty to the charges. A trial date has not been set.
But Cowart's defense attorney claims, in a motion to dismiss the indictment against him, that of the 23 grand jurors who indicted Cowart on November 5, 21 were African-American and two were white.
Attorney Joe Byrd argues in the motion that the case should have been tried in the Eastern Division of Tennessee, where Cowart lives, but federal prosecutors decided to try it in the Western Division.
But in either division, Byrd wrote that "such a degree of under-representation" does not reflect the racial makeup of the area. "The right to an impartial jury requires a fair possibility for obtaining a jury constituting a representative cross-section of the community."
Under that rule, more than 80 percent of grand jurors from the five Tennessee counties encompassing the Western Division should have been from Shelby County, which contains the city of Memphis, Byrd wrote.
Since more than 64 percent of Shelby County residents voted for Obama in the election, he wrote, "the probable cause determination resulting in the defendant's seven-count indictment was handed down by a grand jury which statistically could not have represented a fair cross-section of the community nor which under the most modest constitutional scrutiny could be considered fair, impartial and unprejudiced."
Byrd told CNN that with such a "gross statistical disparity," the court had a responsibility to quiz potential jurors on whether they felt they could remain fair and impartial, given the nature of the case. According to his motion, no such question was asked.
"I'm saying that I think this may be a sign of severe problems," Byrd said.
Cowart and Schlesselman were arrested outside Jackson, Tennessee, about 75 miles east of Memphis, after an aborted robbery attempt, according to court records.
According to an affidavit from the federal agent who questioned them, the two planned to charge at Obama with a car, firing from the windows as they went. They would be dressed in white tuxedos and top hats during the attempt, the affidavit said.
But federal law enforcement sources have said there was no evidence the two had any details of Obama's schedule.
And although they told investigators they would have been willing to die in their mission, they backed out of their October 21 attempt to rob a gun dealer after spotting two cars and a dog at the home, the affidavit states. However, they shot out the window of a church on their way back to Cowart's grandfather's home, where they were arrested the following day.
According to the affidavit, they planned to start their spree by killing more than 100 African-Americans, including 14 who would be beheaded.
One of the federal law enforcement sources told CNN that while the plot was being taken seriously, "we see no evidence these guys have the ability or the wherewithal to pull off what they say they wanted to do."
Obama was placed under Secret Service protection in May 2007, far earlier than other presidential candidates. Threats against him led to arrests in two previous cases.
In one, federal prosecutors said that the three people arrested with drugs and weapons in a suburban Denver, Colorado, motel posed a "true threat" to the candidate. In the second, a Florida man was charged with threatening bodily harm against the candidate in August.
Byrd's motion asks that the indictment against Cowart be dismissed and that the court investigate whether the failure to ask jurors whether they could be impartial resulted in his receiving an impartial jury. The motion also asks the court to appoint a commissioner to interview each of the grand jurors to see if there was any partiality or prejudice on their part.
Prosecutors have 10 days to respond, Byrd said.
CNN's Kevin Bohn contributed to this report.