When Richard Lovelace penned the 17th century love poem that begins "Stone walls do not a prison make", he obviously hadn't been to Liberia's most overcrowded jail. For at Monrovia Central Prison there is little else but crumbling stone walls, rusty iron bars and the stench of rotting dignity.

More than 600 prisoners are held here, five times the jail's intended capacity. They are crammed, sometimes 10 to a cell, inside dark cellblocks where air rarely flows but sewage does.

Among the inmates in the women's block is Mary, a 60-year-old woman arrested for failing to pay a bill on time. She shares a mouldy mattress with seven other women, some of whom are accused of more serious crimes.

Accused is the optimum word. Of the 651 inmates, just 28 have been sentenced.

Liberia's 14 year conflict tore the country's judicial system apart. Four years after the end of the war, it is barely functional. Defendants sometimes wait years just to see a judge. Nobody knows who might be innocent and who might be guilty.

When I walk into the men's block I'm engulfed by throngs of sweaty, hungry men who haven't eaten in hours and haven't seen a woman in months. They pour into the corridor, asking for food, water, mattresses, a phone number.

Among them are 127 men accused of gang rape and several awaiting trial for murder. Others are here for lesser crimes such as petty theft. Some have been locked up because they are gay.

I meet Joseph, a gaunt looking man with a long beard and a cigarette. He arrived four months ago on charges of aggravated assault. He went to court but the alleged victim didn't turn up and he doesn't know if there will be a retrial.

There is BB Smith, the joker of the block, accused of robbery. Since he was brought here he hasn't heard from his family, friends or any judge. He makes people laugh because he doesn't know what else to do.

And then there is Chimba, a giant of a man eager to be listened to. As he proclaims his innocence, his screams ricochet off the urine-stained walls. A judge has offered him bail but he can't stump up the $2,500 fee. Freedom is expensive, he whispers as I leave, but perhaps I could bring him a bucket.

War has really taken its toll on Liberia's prison service. Most of the correctional officers working here are unpaid trainees and only the Nepali U.N. soldiers who man the watchtowers are armed. A brand new block has just been completed with U.N. funding, but the prisoners have yet to move in.

"After the U.N. leave, the government won't be able to support the prison," one of the trainees confides. This week the U.N. mandate in Liberia was extended for one more year.

Because the government's funds are so limited, the corridors are patrolled by the inmates themselves. Amah, an eloquent 28-year-old on rape charges, runs Block B. He serves meals of bulgar wheat twice a day and arranges the weekly laundry run. "We just don't have enough staff," he says. "Or mattresses".

In the prison grounds there is a brightly painted tuck shop selling cream crackers, lollipops and melted chocolate bars. Behind the counter is Peterson, an inmate accused of manslaughter. He's been working in the shop for three months.

"I wouldn't say I like working here, but it keeps me busy," he says, in a slow Liberian drawl. "No one can say if I'll go to court," he adds as he puts torn packets of biscuits on the half-empty shelves.

One of his customers is Jim, a young teenager housed in one of the prison's overcrowded juvenile cells. His voice hasn't broken yet but his childhood is in pieces.

Liberian law says under-16s should not be in prison while awaiting trial, but the country's sole juvenile judge is so overworked that he hasn't found time to house them elsewhere. So they fester - and there is no other word for it - in a hot filthy cell furnished with a potty, half a foam mattress and a broken bucket.

The wind carries their high-pitched cries through the tiny barred windows. I can still hear them as I walk through the heavy black gates. "We are blessed to have the U.N. here," the unpaid officer says as he sees me out.

A few hours here is almost too much to bear. I go home and take a long hot shower. I don't want to imagine how it must feel to be here for weeks, months, years. Somehow I don't think bathing in a bucket of stagnant water would wash away the pain.