By Breaking Celebrity News Staff

Mariah Yeater, the 20-year-old California woman who claims Justin Bieber sired her 5-month-old son, is holding steadfast to her story that the pop singer is the child's father.

When asked by the Chicago Sun-Times on December 14 whether or not ex-boyfriend Robbie Powell -- who was arrested November 26 on drug and burglary charges -- is the real father, Yeater replied, “Yes, I know him.”

But then insisted, "He is not the father, and he’s locked up and out of the picture.”

Yeater told the paper she's still pursuing her paternity claim against Bieber out of court, through her attorneys in Chicago and Los Angeles.

“I dropped my lawsuit, but never my claim. I still definitely want a DNA test and I want to refile my paternity case -- I do believe he is the father,” Yeater told the paper.

While Bieber claims he took a DNA test last month, Yeater's Chicago counsel, Jeffery Leving, told the Sun-Times the pop star’s camp has been sluggish and non-cooperative in getting on the same page as Yeater's, concerning the test.

“Bieber’s counsel hasn’t told me where Bieber’s alleged DNA is se