Shawn Schroeder stepped down from the witness stand in a Fairfax County courtroom yesterday and showed jurors what was left of his mutilated left hand after Mara Salvatrucha gang members attacked him with a machete outside a Merrifield movie theater.

Schroeder testified that he and his girlfriend were leaving the Lee Highway Multiplex Cinemas on Jan. 3 with their baby when a Nissan Maxima pulled alongside them. Schroeder said that Wilber A. Rivera leaned out and yelled, "Don't you remember me from Tysons Corner mall?"

Schroeder said he ran back toward the theaters while his girlfriend headed in another direction with their child. Then Rivera pushed another gang member out of the way and swung a machete at his head, Schroeder said. Before he could escape, someone stabbed him in the arm, shoulder and back.

"They kept swinging the machete at me," said Schroeder, 25, who lost three fingers and has large, visible scars on his head. He said the attackers yelled, "La Mara Salvatrucha!"

Schroeder's testimony came as Rivera's trial began in Fairfax County Circuit Court on charges of aggravated malicious wounding and gang participation. Rivera, 19, pleaded not guilty. Gang member Moris Villalobos pleaded guilty last week in the attack.

Rivera's attorney, David Bernhard, said the evidence will show that his client was "guilty of being from El Salvador . . . guilty of having been seen in the company of Moris A. Villalobos . . . [and] guilty of having a tattoo that says 'MS.' " The tattoo, which police said in court records is on Rivera's chest, was made when Rivera was a child in El Salvador, Bernhard said.

Bernhard said Rivera was a hard-working teenager, employed as a busboy at the Rainforest Cafe at Tysons Corner Center, and spent his nights with his girlfriend. Rivera will contend that he wasn't near the Lee Highway theaters that night but was watching television with his girlfriend.

"He wasn't involved," Bernhard said. "He wasn't there."

Villalobos testified that Rivera was there but that he did not have a machete and swung only a pocketknife at the victim.

Schroeder, the first witness in the trial, emphatically contradicted Bernhard. He repeatedly pointed out Rivera as his main attacker, glared at him from the witness stand and said they had had several confrontations at Tysons Corner, including one in which Rivera supposedly brandished a machete in the mall.

Outside the theaters, "I played like I was dead," Schroeder said, adding that he lay down with one hand over his head. He said that was when the blow that slashed off his fingers came.

Covered in tattoos himself, Schroeder acknowledged that he is a longtime member of the Rollin' 60s, a clique of the Los Angeles-based Crips that has spread across the country. He said he initially told police that he thought the attack was by someone trying to replace him as a Crips leader. The first officer on the scene, Richard K. Bistline, said Schroeder told him that a "Wilber Simmons" had attacked him.

Last week, Villalobos pleaded guilty to aggravated malicious wounding and agreed to testify. He said he knew that Rivera and Schroeder had had previous confrontations. When they spotted Schroeder outside the movie theater, he said, Rivera was the first out of the car in pursuit.

But Villalobos said that Rivera had only a pocketknife and that he didn't see Rivera stab Schroeder. He said someone he knew only as "Little Scorpion" wielded the machete.

Assistant Commonwealth's Attorney John R. Murphy asked Villalobos why Rivera didn't like Schroeder. "Because he's in a rival gang," Villalobos said.

"Do the Crips get along with MS-13?" Murphy asked.

"Some of them," Villalobos replied. "Some don't. Shawn Schroeder doesn't."

The attack on Schroeder was the second debilitating machete attack by MS-13 members in Fairfax in an eight-month span. In May 2004, three MS-13 members cornered a 16-year-old member of South Side Locos and slashed off four of his fingers. All three of his attackers pleaded guilty and were sentenced to 15 years in prison.