NASCAR is calling for a federal judge to reinstate Jeremy Mayfield's drug suspension after it says the driver has again tested positive for methamphetamine.
The positive result from a July 6 random test was included in a U.S. District Court filing Wednesday.
The filing included an affidavit from Mayfield's stepmother, who claims she personally witnessed the driver using methamphetamine at least 30 times over seven years.
NASCAR said in its filings that the "A" sample had levels of methamphetamine consistent with habitual users who consume high doses.
The filing also claims Mayfield and his attorneys have failed to select a qualified laboratory to test the backup "B" sample.