ST. LOUIS • The prosecution of seven juveniles charged with brutally beating a man for sport collapsed this week when a key witness didn't show for the trial, officials said today.

Seven youths, ages 12 through 14, were accused of attacking Matt Quain, 52, of St. Louis on Oct. 21 as part of the so-called "knockout game," leaving him with a broken jaw, black eye and stitches in his face. All had been charged with second-degree assault.

Prosecutors were at the last minute forced to drop the case when the witness, a 13-year-old girl, didn't show for an adjudication hearing Monday in juvenile court. It is the equivalent of a trial in adult court.

A court spokesman, Matt Murphy, said the witness has refused to cooperate further. He declined to comment further about the witness given that it is a juvenile matter.

Quain said that after the hearing the accused teens gathered in the hallway celebrating the outcome.

"They were cheering and high-fiving," Quain said. "It was like a big game to them."

The teens, who had been held in detention pending the hearing, were released immediately afterward.

The chief trial attorney who handled the case, Margaret Gangle, has not yet been reached for comment. A defense attorney for one accused teen declined comment.

Quain and a neighbor were walking home from a Schnucks store on South Grand Boulevard about 11:40 p.m. on Oct. 21. They were a few blocks from their apartment building when a group of teens surprised them near the Carpenter branch public library.

The attackers walked off as Mayor Francis Slay and his bodyguard, city police Sgt. Blaise Peluso, happened by in their car, spotted the aftermath of the attack and pulled over to help.

Slay said he is "disappointed and angry" about the case being dismissed and takes it personally because he and Peluso were there after the attack.

"I feel for the young girl," Slay said. "I mean, clearly, she was intimidated (into) not testifying. We need to support witnesses like we support victims."

Slay added, "The more we band together and support the victims and not tolerate this kind of stuff as a community, the more these thugs can get put away and be punished the way they deserve."

Quain, who was knocked unconscious in the attack, was unable to identify the teens who assaulted him, nor were any of the people who stopped to help him.

The "knockout game" has been described as random, unprovoked attacks on unsuspecting victims, usually by teens who have no discernable motive other than to play the "game."

Quain told the Post-Dispatch he is disappointed with the outcome of the case but not surprised the witness backed out.

"They got away with it," Quain said. "It's the system we've got. Our case just didn't hold water with the law."

Quain said he is concerned about others becoming victims of the so-called knockout game.

"It's disturbing," he said. "I feel bad for the next unsuspecting victim. I don't doubt that they're gonna do it again."

He said it was difficult seeing his alleged attackers, six boys and a girl, in the courtroom Monday morning.

"They were looking me over like I was a piece of meat," he said.

Quain has worked as a dishwasher for more than seven years at Joanie's Pizza in Soulard. He returned to the shop on a part-time basis two weeks ago and hopes to return full-time as soon as he fully recovers from the attack.

"It's my second family," he said of the restaurant staff.