They studied philosophy in college and read poet Osip Mandelstam -- a Stalin critic who died of typhoid in a labour camp in 1938 -- for inspiration.

Now the three members of all-girl punk band Pussy Riot face the prospect of spending three years in a corrective labour facility for entering a huge Moscow church and denouncing President Vladimir Putin in a raucous song.

Most of the song dealt with the marginalised role of women in Russian society and the dominance Putin has established over politics since rising to power 12 years ago.

The group also attacked the Church's backing for Putin and hinted of its tie to the secret police.

A judge will start reading her verdict on Friday with both the Kremlin and critical Western governments keeping a close watch.

The three punk rockers in their 20s and 30s have apologised for offending the Orthodox faithful but not for their political views.

The band was formed in August 2011 and soon grabbed headlines with impromptu performances of political protest songs played on air guitars in busy places such as subway stations and even Red Square.

They wore homemade balaclavas with neon dresses over clunky boots for maximum impact and danced with wild abandon.

The US pop icon Madonna said she prayed for the three Pussy Riot women because "they have done something courageous (and) paid the price".

--- Nadezhda Tolokonnikova, 22

The singer was born in one of the most inhospitable places on Earth -- the Norilsk nickel mining city above the Arctic circle that Stalin developed using Soviet prison labour.

She studies at Russia's top-rated Moscow State University and has a daughter with her husband Pyotr Verzilov who has backed the group's cause.

Both are also members of the controversial Voina (War) performance art group that won a prestigious Russian prize for painting a 65-metre (210-foot) phallus opposite a security service building in Putin's native Saint Petersburg.

She compared her hearing to the tribunals Stalin used to conduct his bloody political purges in the 1930s and told the judge that the three members "expect to remain (behind bars) for a very long time to come".

--- Maria Alyokhina, 24

The single mother of a five-year-old son is a Greenpeace member who has campaigned and scuffled with the police in the past during a group of green activists' passionate defence of a small forest outside Moscow.

The campaign against the road building there proved fertile ground for Russian political activism by developing many of the leaders who spearheaded opposition to Putin's return to a third presidential term earlier this year.

Alyokhina's software-engineer mother recently revealed that her daughter was also religious and was only protesting against the Church's open backing for Putin.

She said her daughter spent much of her time teaching creative arts to traumatised children at a Moscow psychiatric hospital.

Alyokhina's final court statement condemned Russia as a place where only "so-called freedom" exists.

--- Yekaterina Samutsevich, 30

The eldest of the three worked on designing computer software for the Nerpa class nuclear submarine after graduating from a Moscow physics institute.

She left to study photography and eventually graduated from a Moscow multimedia centre.

She joined the Voina performance art group at the same time and was regarded as one of the most active members of a March 2011 campaign to kiss as many policewomen as possible in public.