Opposition demonstrators hold posters of imprisoned protesters during a major protest rally in Bolotnaya Square in Moscow, Russia, Monday May 6, 2013. The rally marks the one-year anniversary of a protest on the eve of Putin's inauguration that ended in clashes between police and demonstrators. AP Photo/Alexander Zemlianichenko FILE- In this Monday, April 22, 2013 file photo, opposition activist Konstantin Lebedev charged with instigation of mass riots during last May's rally against Vladimir Putin's return to the Kremlin, listens to his lawyer in the Moscow City Court before a court session in Moscow, Russia. Lebedev pleaded guilty and testified against opposition leaders, including leftist leader Sergei Udaltsov. More than two dozen people are facing criminal charges over their alleged involvement in the May 6, 2012 opposition protest that ended in violent clashes between demonstrators and police. AP Photo/Yevgeny Feldman, FILE Opposition protesters listen to a speech during a major protest rally in Bolotnaya Square in Moscow, Russia, Monday May 6, 2013. Up to 20,000 Russian opposition supporters gathered for a protest on Monday, venting anger against the Kremlin and demanding the release of political prisoners. The protest came exactly one year after a demonstration a day before President Vladimir Putin's third presidential inauguration on the same square near the Kremlin ended in violent clashes between demonstrators and police. Russian riot police secure an area outside the Kremlin during a major protest rally in Bolotnaya Square in Moscow, Russia, Monday May 6, 2013. Opposition protesters hold a poster of opposition leader Sergei Udaltsov, right, who is under house arrest, and other imprisoned oppositions, during a major protest rally in Bolotnaya Square in Moscow, Russia, Monday May 6, 2013. MOSCOW (AP) - About 20,000 protesters thronged Bolotnaya Square across from the Kremlin on Monday, a year after a protest at the same spot turned violent on the eve of President Vladimir Putin's inauguration. Monday's turnout - far less than the 100,000 or more who marched through Moscow with giddy optimism ahead of Putin's election to a third term - reflected a wariness that has sapped energy from the protest movement. As a result of last year's protest, 27 people face charges that could send them to prison for up to 10 years. Some are battle-hardened opposition activists, but just as many are ordinary Russians who had joined anti-Putin protests for the first time last year. Portraits of the prisoners and officials involved in the case lined the stage Monday, while several speakers read letters that the defendants sent from jail. Here is a look at some of the people involved: The youngest of the defendants at 19, environmental activist Dukhanina has spent the past year under house arrest, allowed visits only from her lawyers and close relatives. Investigators have charged her with throwing rocks and bottles at riot police, although they later found that the policeman listed as the victim in the case was unharmed. She faces up to eight years in prison. A first-year student and former marine, 21-year-old Lutskevich was attending his first protest. When riot police seized a female friend of his, Lutskevich said he tried to help her. He was beaten so severely that his body was still covered in red welts when he appeared in court. Investigators accused him of throwing pieces of asphalt at police and ripping off one of their helmets. He has been in jail since June and faces up to eight years in prison. Arrested at the protest in a black suit jacket and tie, leftist activist Akimenkov, 25, is accused of trying to break through a police barrier and hide in the crowd. While behind bars, a serious eye condition he suffers from has significantly worsened to the point that he is almost blind. Despite notes from doctors that he should not be held in jail, Akimenkov has been denied bail. He faces up to eight years in prison. The commercial director of a tourism firm whose only activism had been to help stray animals, Arkhipenkov was detained while walking out of a metro station near the protest. Despite having had no plans to take part in the protest, Arkhipenkov was held in prison for two months, where his lawyer said he was forcibly injected with unspecified psychiatric medication. He was later released on bail and faces up to eight years in prison. A gym owner and bodybuilder who has never been part of any political movement, Luzyanin was subdued with a stun gun, arrested and held incommunicado for two days after investigators found photographs of a masked man with Luzyanin's rippling physique fighting policemen. Luzyanin, 36, entered a guilty plea and paid the dental bill of the policeman whose tooth he was accused of chipping. He was sentenced to four and a half years in prison. Lebedev was arrested in October after state-controlled television ran a documentary-style film purporting that he and two other activists, including leftist protest leader Sergei Udaltsov, had met with Georgian officials to organize terrorist attacks and the violent overthrow of the government with money from rogue oligarchs in London. Lebedev initially denied the accusations, but pleaded guilty earlier this year, testified against the two other activists, and was sentenced to two and a half years in prison. Former associates have accused him of serving as a stooge to undermine the protest movement. Udaltsov, who remains under house arrest, faces up to 10 years in prison.