It began with a rule any child can recite: Don't cut in line.

When Leah Talak broke the women's bathroom line at Diesel, a South Side club, the women in front took offense.

Although Ms. Talak said she wasn't going to use the bathroom and was only looking for a quiet place to make a phone call, a profane exchange ensued. Ms. Talak was knocked to the floor, hit with a metal pipe and repeatedly kicked in the face, according to testimony this week from Ms. Talak and other witnesses.

When she emerged from the club, Ms. Talak identified Stephanie Bannon as her attacker. Ms. Bannon insisted it was another friend of hers, who left through the back door.

Yesterday, an Allegheny County jury sided with Ms. Bannon, 26, of Beaver Falls, finding her not guilty of aggravated assault and simple assault.

Defense attorney Wayne DeLuca in his closing argument said police rushed to charge Ms. Bannon on the victim's word and didn't canvass for witnesses or search for Ms. Bannon's friend.

"This is not what I'd call a thorough investigation," Mr. DeLuca said.

On July 21, 2007, Ms. Bannon was waiting to use the bathroom at Diesel with a group of friends when Ms. Talak cut to the front.

Ms. Bannon testified that she turned to her friends and asked, "Who does this girl think she is?"

Then Ms. Bannon and her crew started jawing with Ms. Talak. Ms. Bannon said she left the altercation when a stall came open.

She came out to see Ms. Talak in a bloody mess on the floor, Ms. Bannon testified, and her friend kicking the victim in the head. Ms. Bannon said she then went outside to tell the police what was going on.

Ms. Talak, 30, testified that her assailant was Ms. Bannon, and she was backed up by bathroom attendant Annette Williams, who also identified Ms. Bannon.

Several of Ms. Bannon's friends, meanwhile, testified in support of her account.

And Mr. DeLuca brought in a forensics expert, who testified that there was no blood on Ms. Bannon's clothes or the high-heeled black patent leather shoes she was wearing that night. In his closing argument, Mr. DeLuca attacked police for not doing any forensic testing of their own.

Assistant District Attorney Summer Ford, in her closing, brandished Ms. Bannon's jail mugshot, in which she is smiling in what appears to be a pose for the camera.

"Does this face look like someone wrongly accused of aggravated assault?" Ms. Ford said. "Now wipe that smirk off her face and find her guilty."

When the not guilty verdict was announced, Ms. Bannon exhaled deeply. She exchanged tearful hugs with her friends and Mr. DeLuca in the hallway.