Jeremy Mayfield didn't spare his stepmother or NASCAR while defending himself against Wednesday's report that he again has tested positive for methamphetamines.

NASCAR filed court papers on Wednesday that said his most recent drug test came back positive, and included an affidavit from Mayfield's stepmother, Lisa, who claims to have seen the driver using drugs on numerous occasions.

Mayfield said he does not trust NASCAR testing and saved his strongest words for his stepmother.

"She's basically a whore," he told ESPN.com's David Newton. "She shot and killed my dad."

Mayfield's father, Terry, died in 2007 at age 56 of what the Chapel Hill, N.C., medical examiner called a self-inflicted gunshot wound to the chest. There was no sign of criminal activity or foul play, according to the sheriff's report, which noted Lisa Mayfield said Terry Mayfield was "very depressed about not talking with his son, Jeremy, that this was only a matter of time."

Nevertheless, Mayfield told ESPN.com on Wednesday that his stepmother will be served with a wrongful death suit. Mayfield said he went to his attorney on Thursday to start proceedings and plans to file on or before Aug. 15.

"She knows what we've got on her," Mayfield said. "For her to come out and do this is pretty ballsy. Everybody that's ever known me knows I never, ever have been around her for more than 10 hours of my life. She's a gold digger. I knew that from day one."

Although he said he has no proof, Mayfield claimed that NASCAR paid Lisa Mayfield for her affidavit.

"It wouldn't take much money. She tried to get money from me," Mayfield said. "I have a very short fuse when it comes to her."