The 25-year-old sales manager got caught up in an investigation into what Russian authorities describe as rioting. Fourteen people were charged, mostly random protesters with no history of political activism. Analysts say the probe is an attempt to crack down on anti-Kremlin dissent with trivial accusations that range from throwing the cup to directing the crowd to step off the pavement.
Vyacheslav Abanichev was at his family's summer cottage outside Moscow when his son called to say that a group of unknown men were banging on the door of the family's apartment. Only hours later did the man who eventually knocked down the door identify the group as police officers and investigators.
The Abanichevs did not know what to think when they were told that their son was a witness in a rioting case. Later that day, he came out of a meeting with investigators and told his parents that he was identified in a video from the July 27 protest as someone who threw a beer can at police.
"He had an empty paper cup," the elder Abanichev said, quoting his son's account. "He told us that the police were trying to push out the crowd, and that he threw out the cup, and that was that." Later that day, his son was named a suspect in the rioting case and taken to jail. On Aug. 3, a court ruled that he must stay in custody for two months during the probe.
"When he remembered about that paper cup, I was baffled," the father said. "I'm still baffled. I can't understand what they're keeping him, a random person, in jail for." Anti-government protests erupted in Moscow in mid-July after election officials barred a dozen opposition candidates from running for the Moscow city legislature. Authorities originally allowed the weekend protests to go unhindered but later outlawed the gatherings and started detaining and beating the demonstrators, which only helped to swell the crowds.
On July 27, thousands thronged the area around Moscow's main drag where authorities deployed a formidable riot police force. Officers were seen detaining and often beating men and women alike. In frustration, some bystanders hurled plastic bottles at police, and some tried to force their way past police lines.
Protesters were not seen attacking the police. No property damage was reported either. Yegor Zhukov, a 21-year-old student and blogger, is now in jail for at least two months after investigators said they have footage of him directing the crowd off the pavement and onto a busy street.
Valery Kostenok, a 20-year-old student who had been collecting signatures for one of the candidates, was arrested and charged with rioting after investigators claimed that he threw two empty plastic bottles at police. Kostenok admitted later in court to throwing the bottles in anger but insisted that the empty bottles could not hurt anyone.
Danil Beglets, a 26-year-old bed salesman, said in court that he ended up in the crowd by chance. When he saw a man being detained, he reached out to pick up headphones the man must have dropped. The prosecutors allege that Beglets, a father of two, pushed a riot police officer.
Details in some case files appear to be sketchy, but some of the suspects are in custody without even knowing what they are accused of. Maxim Pashkov, lawyer for 25-year-old information technology engineer Aidar Gubaidulin, said he does not know how to defend his client.
"There's nothing specific in the indictment," he said. "It just said he 'took part in the riots, tried to break the police lines.'" Pashkov heard about a can thrown by Gubaidulin but said that allegation is nowhere to be found in the files he viewed.
Gubaidulin, originally from the Ural mountain city of Ufa, went out on July 27 to protest the authorities' decision to disqualify opposition candidates "because every person should have the right to be elected," his mother, Galiya, told The Associated Press.
Days later, dozens of family members, friends and former classmates flocked to a Moscow courtroom to cheer on Gubaidulin, who appeared in court via a video link from jail. Without reciting or requesting details of what Gubaidulin is suspected of, the judge upheld a lower court's decision and ruled to keep him in jail for two months.
Gubaidulin's frail mother, who traveled to Moscow to attend the hearing, is outraged about what happened to her son, the pride of the whole family, who moved to the capital, graduated from Russia's most prestigious physics school and found a lucrative IT job.
"It's a nightmare. It's a travesty. It's a joke," Galiya Gubaidulina said, choking on tears after the hearing. "If you get down to the details, they are prosecuting (him) for nothing." The charges appear to be meant as a warning to anyone considering coming out at an impromptu protest, rather than a personal vendetta, analysts said.
Moscow-based political analyst Ekaterina Schulmann said the case against the protesters does not look like part of the Kremlin's long-term strategy. It's more of a scare tactic to affect the size of the crowds that have been gathering nearly every weekend for almost two months.
The arrests did not keep the suspects' families off the streets. Sergei Abanichev's father and his father's wife went to an authorized protest on a wet, chilly afternoon with a poster listing the names of those facing the rioting charges under the slogan "Freedom for my son!"
Abanichev was opposition-leaning before, but he said that Sergei's arrest showed him just how unfair Russia's law enforcement system is. The rioting case involving 14 people is being investigated by 80 top investigators, the families of the suspects were told.
"It's 80 people, can you imagine?" Abanichev said, speaking at the family home where his son's room stands empty. "They're working thanks to our taxes investigating a paper cup."
Associated Press Writer Francesca Ebel contributed to this report.