CHARLOTTE, N.C. -- NASCAR has confirmed suspended driver Jeremy Mayfield tested positive for methamphetamines.

The confirmation from NASCAR spokesman Ramsey Poston came Wednesday after Mayfield's attorney mentioned the illegal substance several times during a 45-minute argument against the suspension.

Mayfield has denied using methamphetamines. He's in federal court in Charlotte, N.C., trying to have his suspension lifted in time to race this weekend at Daytona International Speedway.

Mayfield lawyer Bill Diehl argued that NASCAR's testing system is flawed because Mayfield was never given the opportunity to have his backup "B" sample tested by an independent laboratory.

The court recessed after Diehl's argument and will reconvene at 2 p.m.