Florescu for NewsJennifer Mercado of the Bronx hides her face. She used the credit cards of fellow juror John Postrk (inset) for a $500 shopping spree.

Chu for News

Jennifer Mercado is accused of swiping a fellow juror's American Express card and using it at to buy four pairs of shoes, including Nike Air Jordans.

There was more than one criminal in this courtroom.

The Bronx trial of an accused credit card thief was thrown into turmoil when a juror's plastic was stolen and used for a shopping spree - allegedly by another juror!

Jennifer Mercado, 20, went from sitting in judgment to sitting in a cell after she brazenly waltzed in from lunch breaks loaded down with bags.

The prosecutor of the trial - which also involved a stolen credit card - helped nail her by reviewing the store's security video.

Mercado doesn't deny she used fellow juror John Postrk's American Express card to buy more than $500 worth of loot, but she apparently didn't learn much about reasonable doubt while doing her civic duty.

"The guy did give me permission to use his credit card," she told the Daily News.

Asked why Postrk would do that, Mercado came up with an alibi worthy of "Law & Order."

"He came on to me," she said. "It's a he-said, she-said situation. In court, they will find out he's lying."

Postrk, 49, who works for the Children's Aid Society, said prosecutors asked him not to talk about the case.

He and Mercado were sitting on the trial of Warren Stewart, arrested in 2006 for burglary, grand larceny and possessing a stolen credit card.

On March 8, Postrk's American Express cards and MetroCard were swiped from his coat, court documents charge.

That day, and the next two days, his card was used at local stores during jurors' lunch hour.

When Postrk reported the theft to the judge on March 10, he already had a suspect in mind because the charges on his American Express account came from stores where Mercado had been shopping.

"It's the person that came back with the baggage," Postrk told Judge Barbara Newman.

He noted that a court officer commented on Mercado's bags.

"As we were leaving one of the court officers mentioned, 'Oh, that's a really nice bag,' " Postrk said. "And I just happened to look. And she did a double-take back, like I scared her."

Assistant District Attorney Jacob Kaplan, who was prosecuting Stewart, investigated Postrk's claims during a recess.

With another prosecutor and investigator, he went to stores across from the Bronx Hall of Justice and viewed videos of a woman who appeared to be Mercado using Postrk's card, court transcripts say.

Twenty minutes later, Mercado came back to one of the stores and tried to make a purchase. A manager asked her for ID and she apparently got spooked.

"She pulled out what [the manager] believed to be another American Express card in what he believed was John Postrk's name," Kaplan told the judge.

"And when he turned around, she dropped the credit card and walked out of the store."

At the Jeans Plus shop, Mercado made quite an impression, buying four pairs of shoes, including a pair of Nike Air Jordans.

"She was talking nice to me, asking for a discount," manager Jason Ayoub said.

Mercado was arrested March 12 and charged with grand larceny, stolen property, identity theft and unlawful use of a credit card. She faces four years.

Her lawyer declined comment.

Mercado was removed from the Stewart case but Postrk stayed. The jury acquitted Stewart of having a stolen credit card, but convicted him of burglary.

Stewart's lawyer, Soraya Hurtado, asked for a mistrial because of the incident but was denied.

The district attorney's office declined to comment, but word of the case spread quickly.

"You've got to be really stupid to do that in front of a judge, court officers, law enforcement and all the cameras in this building," said one courthouse employee.