NATE WELLS says the encounter started out as "busting" - ribbing someone over his or her fashion sense.

It ended with his buddy "Zeem" lying on the pavement on Watkins Street near 21st in Point Breeze, bleeding from a stab wound to his chest.

Yesterday, Wells, 14, laid out his account of what led to the fatal stabbing of Azim "Zeem" Chaplin, 14, on that night in February during a preliminary hearing for Chaplin's alleged killer.

And after a heated testimony, Judge James M. DeLeon approved third-degree-murder charges for that suspect, Amber Hellesten, a girl one year Chaplin's senior. She'll stand trial May 13.

David Desiderio, Hellesten's attorney, argued that the charges should be dropped. He told DeLeon that his client had acted in self-defense after being harassed and followed by three boys she didn't know.

DeLeon, upon hearing Wells' account, didn't rule out that argument.

"This is a confrontation that lasted for 5 1/2 blocks," he said. "Kids don't just bust on strangers; that's like gang behavior."

According to Wells' testimony, he, Chaplin and their buddy "Sheefy" encountered Hellesten and one of her friends as the two groups were walking in opposite directions on Snyder Avenue near 19th Street.

The boys, who were headed to another girl's house, started "busting" on the girls about their clothes and sneakers, Wells said. They didn't know each other, and, when pressed by Desiderio, Wells couldn't provide an explanation for why he and his pals chose to taunt the girls.

He said that it began good-naturedly, and that the girls laughed and taunted them back. But then the guys starting throwing ice and snow at the girls, and followed them as they turned down a side street.

Finally, an agitated Hellesten threatened to have "her brother kill" Chaplin, Wells said.

The girls walked away, and Chaplin and Wells, reeling from the threat, armed themselves with sticks, the youth said. When Chaplin walked toward Hellesten, looking to throw his stick at her, the girl pulled out a black pocket knife from her purse, Wells said.

Wells said Chaplin raised his stick, ready to swing. Hellesten thrust her knife into his chest, striking him between his fifth and sixth ribs, according to a report from the Medical Examiner's office read during the hearing. The blade punctured his heart, and he died five days later at Children's Hospital of Philadelphia.

"Any thinking person can see that it was self-defense," Desiderio told reporters after the hearing. "It's a matter of someone who's cornered swinging at the stranger who's cornered her."

He said his client, who has an "abusive past," started carrying the knife after a previous assault.

Assistant District Attorney Gwenn Cujdik, who's handling the case, described the situation as typical teenage behavior that "became something deadly."

Hellesten "knew she had the knife the whole time," Cujdik said. "These kids came into something that was a surprise to them."

Hellesten remained in custody last night, her bail set at $150,000.

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