According to baby mama Mariah Yeater's lawyers, there is credible evidence that Tristyn Anthony Markhouse Yeater is Justin Bieber's baby.

The 20-year-old mother is pursuing a modest and rightful claim from the 17-year-old Canadian pop star. Yeater claims to have had casual intercourse with Bieber at a concert at Los Angeles' Staples Center last October - the same place Bieber recently rented out to watch Titanic on the Jumbo-tron with his current girlfriend Selena Gomez.

Yeater filed the lawsuit on Oct. 31, claiming that Bieber's bodyguards invited her backstage after a Los Angeles performance. He's said to have told the fan that it was his first time before quickly removing his clothes. Yeater claims that the liaison lasted about 30 seconds in a backstage bathroom.

Yeater states in court papers obtained by Star magazine that she gets food stamps and welfare totaling about $500 per month and has just $400 in the bank. She claims to owe the hospital where she gave birth $25,000. She also recounts a salacious blow-by-blow of how her son was conceived and maintains that she contacted Bieber's representatives after she got pregnant, but never received a call back.

Bieber, a devout Christian who's spoken out against casual intercourse in the past, went into overdrive to protect his wholesome reputation.

On Wednesday, he tweeted: all the rumors... the gossip... I'm gonna focus on the positives... the music.

The Canadian pop star would have been 16 at the time of the incident - and Yeater 19. If her claims are true, she leaves herself vulnerable to possible prosecution for statutory rape of a minor as California's age of consent is 18.

Bieber's spokesman said that they will pursue all available legal remedies to protect him against the allegations.

Despite the fact that Bieber's publicists have called the lawsuit a fabrication, defamatory and malicious, Yeater's lawyers added Wednesday night that they have credible evidence behind the claims.

Yeater's lawyers, Lance Rogers and Matthew Pare, said in a statement that their client was not looking to amass a large sum of money, but wanted support for her child.

[She] is pursuing a modest and rightful claim, the lawyers said as the new edition of Star magazine hit the shelves with Bieber's alleged son on the cover.

We call upon Justin Bieber and his attorneys to reach out and resolve this issue in a reasonable manner, the lawyers added. There is credible evidence that Justin Bieber is in fact the father of her baby.

Yeater has reportedly requested that the court force Bieber to take a paternity test and provide adequate support for the four-month-old baby, born on July 6.

A court date has reportedly been set for Dec. 15.

For now, most of Bieber's fans stand by his side. They excoriated Yeater on Twitter yesterday with Beliebers Believe in Justin tweets, calling the unemployed 20-year-old a whole host of foul names.

Bieber is worth an estimated $85 million. This is the first major scandal the star has faced in his young career and, even if the allegations turn out to be untrue, it could devastate his wholesome image.

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