A Fairfax County jury convicted a 19-year-old member of the Salvadoran gang Mara Salvatrucha yesterday in a January machete attack on a rival gang member that severed three fingers on the rival's left hand.

The jury then sentenced Wilber A. Rivera of Falls Church to 23 years in prison for aggravated malicious wounding and five years for participating in a gang. On Dec. 9, Fairfax Circuit Court Judge Jonathan C. Thacher will decide whether the two terms should run consecutively or concurrently. Under state law, Thacher has the option of reducing the jury's sentence, but he cannot increase it.

The machete attack outside a Merrifield movie theater was the second involving the gang, also known as MS-13, in an eight-month span in Fairfax and heightened fears of escalating gang violence in the region. In the first attack, in May 2004, a member of the South Side Locos gang lost four fingers. Two MS-13 members were sentenced to 15 years in prison, and a third received a 12-year term.

The victim in the January case, Shawn D. Schroeder, 25, has acknowledged that he is a longtime member of the Rollin' 60s, a clique of the Los Angeles-based Crips gang, and prosecutors acknowledged that he was not the most sympathetic victim. "You don't have to condone Mr. Schroeder's lifestyle," Assistant Commonwealth's Attorney John R. Murphy told the jury in his closing argument. "But we don't let people hack each other to pieces on street corners. And we don't say it's okay because it's another gang member getting hacked."

Schroeder testified that he and his girlfriend were leaving the Lee Highway Multiplex Cinemas with their baby the night of Jan. 3 and were heading toward Gallows Road when a Nissan Maxima pulled up. According to Schroeder, a man stuck his head out the window and said, "Don't you remember me from Tysons Corner mall?" Schroeder said he recognized the man from encounters at the mall.

The four men inside the car jumped out and chased Schroeder, who ran back toward the theaters while his girlfriend took their child to safety. Another man, Moris A. Villalobos, testified that he was part of the group that pursued and attacked Schroeder and that Rivera was the first one out of the car.

Schroeder said that one person stabbed him and that Rivera was wielding a machete and hit him in the head. Schroeder stood in front of the jury box to show jurors the long scars across his head and his mutilated left hand.

He said he eventually lay down in front of the theaters and tried to play dead with his left hand over his forehead. He said it was then that Rivera brought the machete down and slashed three fingers off.

Villalobos, who pleaded guilty to the attack last week, testified that Rivera did not have the machete but a much smaller knife. He said another MS-13 member, whom he knew only as "Little Scorpion," wielded the machete. That person has not been arrested.

Murphy told the jurors they did not have to determine who swung which weapon, only whether Rivera participated in the attack.

Rivera did not take the stand in his defense. His attorney, David Bernhard, said Rivera moved to the United States three years ago from El Salvador to escape gang violence there. It was in El Salvador that Rivera had "MS" tattooed on his chest, and he said Rivera had become a law-abiding resident who worked as a busboy at Rainforest Cafe at Tysons Corner Center. Bernhard said he believed Rivera was in the country legally.

Rivera's girlfriend and mother provided his alibi: Both testified that Rivera was doing his laundry at his girlfriend's house on the night of the incident. The girlfriend, Sandra Reyes, said it was not unusual for her to do laundry about 10 or 11 p.m. She said she recently gave birth to a child fathered by Rivera.

Rivera's mother, Maria Rivera, testified that she called her son at Reyes's apartment in Woodbridge at 10:45 p.m. on Jan. 3. The attack happened shortly before midnight.

Murphy noted that Reyes had changed her story -- and Rivera's alibi. When she was interviewed by Detective Chris Flanagan in February, she told him that she and Rivera spent that night at his mother's house watching videos between 7 and 9 p.m., but she would not discuss his whereabouts late that night, Flanagan said.

The jury deliberated for about 90 minutes before convicting Rivera and then spent about 90 minutes devising the sentence. The penalty range was 20 years to life on the aggravated malicious wounding charge and up to 10 years on the gang participation charge.