Packed into old, vermin-ridden cells, often suffering from disease or mental problems, inmates craft makeshift daggers from canteen forks and resort to self-mutilation to pass the time.
One man decapitates his cellmate with a pocket knife. Another dies when his cellmates set fire to a mattress. Rapes are commonplace and there are too few guards to prevent them.
Such scenes, related by a prison warden, illustrate the "descent to hell" that a new report says is taking place in France's prisons as the number of inmates soars under the government's vote-winning crackdown on crime.
And this despite damning reports three years ago which prompted the then French government to describe its prisons as a national disgrace and vow to improve conditions.
"We had reason to fear a deterioration of the situation denounced in 2000 by two parliamentary assemblies, but we did not imagine having to describe a descent towards hell," wrote Thierry Levy of the French-based International Prisons Observatory (OIP) in the report.
Overcrowding has worsened under the center-right's crime drive, the OIP says, with as many as 61,000 people crammed during the summer into cells meant for 48,000 in crumbling penitentiaries.
Around half of those held have not been convicted but are awaiting trial. There is also an acute shortage of wardens.
"We have prisons filled to double capacity and a shortage of 3,000 guards. At night that means three-hour gaps between cell checks and unfortunately a lot can happen in that time," said Remy Carrier, deputy head of the FO prison guard union.
"It goes from minor disturbances to serious attacks. There was one inmate who decapitated his cellmate with a pocket knife. We often can't intervene in time because of the lack of staff."
Intervening can also put wardens, who are unarmed, in danger. A warden in a Paris prison lost her sense of smell, taste and the hearing in one ear after she was beaten by an inmate earlier this year, Carrier said.
"We are confronted with more and more problems," he added. "When things turn violent, it's the warden who is first in line."
When Jean-Pierre Raffarin's conservative government took power last year, the prison population totalled 48,600.
The crime crackdown, which Raffarin placed high on his election manifesto to win back voters who had defected to the far-right, has pushed that up to an average of 55,400 this year.
The OIP found four inmates sharing floor space of just three square meters for up to 23 hours a day, leading to squalor, depression, bullying and violence.
Suicides rose 20 percent to 122 last year and numbered 73 in the six months to July this year.
As newspapers seized on the report, Justice Minister Dominique Perben denounced it as "excessive and grotesque".
Bad press over prisons is the last thing the government needs after taking a battering in opinion polls over unpopular pension and health reforms and a failure to react fast enough to a summer heat wave that killed 15,000 mainly elderly people.
Prison wardens say the OIP report is sensationalist and exaggerates staff misconduct. But they agree action is needed and complain that plans to try alternative punishments for petty crime have come to nothing.
More than half of France's 185 prisons are over a century old and some cells are too dilapidated to use. A spate of brazen jailbreaks in recent years underlined how poor security is.