CHARLOTTE, North Carolina (AP) — An independent drug test on Jeremy Mayfield was negative for methamphetamines, contradicting the results of a NASCAR test taken 40 minutes earlier, the driver claimed in court documents filed on Tuesday.

In response to NASCAR’s claim that Mayfield again tested positive for methamphetamines on July 6, Mayfield submitted an affidavit to the U.S. District Court that said he traveled to Frye Regional Medical Center in Hickory right after NASCAR collected a sample at his Catawba County home.

Mayfield said in the court filing he received confirmation from Laboratory Corporation of America in Raleigh that his sample was negative on July 10 — the same day NASCAR informed his counsel that its sample was positive.

He said the results of his test are “consistent with my lifestyle as I have not and do not use or abuse methamphetamines.

“It is impossible for methamphetamine to be in my body as I have never consumed that substance.”

Dr. Harold Schueler of the Broward County Medical Examiner’s Office in Florida, filed an affidavit on behalf of Mayfield that claimed the levels of methamphetamine in NASCAR’s test are “astronomical” and “could be remotely accurate, unless Mr. Mayfield was deceased or a chronic abuser.”

The filing also denied accusations made last week by his estranged former stepmother, who said in her own affidavit she witnessed Mayfield use methamphetamines at least 30 times and that the driver cooked it himself until the ingredients became too hard to obtain. She also said she witnessed him use the drug at Darlington Raceway in 1999.

“Lisa Mayfield’s assertion that I used methamphetamine just prior to the 1999 Darlington race is a lie,” Mayfield wrote. “I finished second in the 1999 Darlington race.”

Mayfield was suspended on May 9 for failing a random drug test taken eight days earlier for what NASCAR has said was a positive test for methamphetamines. The driver sued, and a federal judge issued an injunction on July 1 that lifted his suspension based on the argument that NASCAR’s testing system is flawed.

NASCAR asked U.S. District Court Judge Graham Mullen last week to reverse the injunction based on new evidence — the failed July 6 test and Lisa Mayfield’s sworn testimony.

Mayfield’s attorneys on Tuesday argued in their response that the July 6 test results — positive or negative — should not be taken into consideration because the case is about a failed May 1 test.