Justin Bieber may have to submit to a new DNA test.

The lawyers for the woman who has accused the 17-year-old singer of being the father of her three-month-old baby claim that the test he took last Friday is not valid because they were not there.

Mariah Yeater, 20, alleges that she had a "30-second" rendezvous with Justin backstage at one of his concerts last year resulting in her getting pregnant.

Justin maintains that the woman is making up the story but submitted for the DNA test to silence critics once and for all that he fathered baby Trystan.

TMZ reported that the tests conducted in New Jersey were done under "very controlled circumstances" and Justin confirmed yesterday that he had his "mouth swabbed."

"I think I could smell a weasel too, a little bit," Justin told David Letterman. "It's pretty crazy, people make up false accusations."

But Mariah's lawyer Jeffrey Leving has told E! News that they are requesting for the test to be done over to confirm that the sample is truly from the pop star.

"We have been negotiating a DNA test," Jeffey said. "We just received communication from Justin Bieber's lawyer today concerning our discussions, which are private."

"I wasn't aware Justin Bieber was allegedly taking a DNA test until I read about it. I don't know if it was even his DNA. Evidence has to be properly supervised to make sure it is not corrupted.

"What I am hoping is to get DNA testing done for everybody and to have it done in a supervised setting."