Three members of an all-girl punk band voiced regret Monday for causing offence when they played an anti-Vladimir Putin song in Russia’s top Orthodox cathedral, but said at their trial they were innocent of their charges. The three young women — who face up to seven years in jail if found guilty of hooliganism charges — said they had wanted to change Russia with their action but could have made an “ethical” mistake by offending worshippers. Initial hearings in the trial earlier this month saw the court order the three members of punk rock group Pussy Riot to stay in detention until January 2013, a move their supporters condemned as travesty of justice. With the initial hearings now over, Monday’s audience saw first legal arguments in the packed Khamovnichesky court in Moscow at a process that is growing into a landmark event in the struggle between President Putin and the emboldened opposition.