In the third of a series of articles looking at policing in Nigeria, the BBC's Andrew Walker visits a prison in the south-eastern city of Enugu where some people who have not committed any crime are locked up for years on end:
"Welcome to the asylum!" says prison warder Iroha Uka, cracking a broad and toothy grin.
We are in a section of Enugu Prison where the state prison service keeps what it calls its "civil lunatics".
These are people who have been taken to court, either by the police or their families, and a magistrate has jailed them - indefinitely, sometimes for life.
A dozen men live in filthy cells like this in Enugu Prison
Usually they have committed no crime, or very minor ones that may not merit a custodial sentence anywhere else in the world.
But the colonial-era law allows Nigerian courts to jail the mentally ill.
Prisoners' Rehabilitation and Welfare Action (Prawa) is an organisation working to get "civil lunatics" released from Nigeria's jails.
They have had 54 mentally ill inmates released from Enugu Prison since 2007.
But there are still hundreds of others in already overcrowded jails all over the country.
Enugu's prison asylum is three tin-roofed sheds, split into separate "wards", rooms filled with rows of bunk beds.
They are hot as ovens and dirty beyond belief.
Most of the day the people are locked inside because there are not enough warders to prevent them escaping.
The men sleep on threadbare foam mattresses or on woven mats on the concrete floor.
"None of these people will get any better here," says nursing officer Michael Aroh.
"They need to be in a hospital environment, not a prison."
A man approaches us and starts to yabber incoherently.
Everyone around him laughs as he struggles to form words that mean anything.
The distress in his eyes is clear, but he cannot stop the torrent of meaningless words that pour out of his mouth.
Suddenly he gains a grip of his language and says his name is John and that he has been incarcerated for nine years.
"I'm [in] difficulties here, I need help! They are detaining me here!" he says before slipping again into gobbledegook.
Mr Aroh says John is actually called Uguchukwu Onaga and he suffers from schizophrenia.
"His mother got tired of him and stopped coming to visit about four years ago."
Another inmate, 26-year-old Ifeanyi, claims he was tricked into being sent to prison in February - possibly by his family.
A small boy brought him some marijuana and then the police arrived and arrested him.
"I have a wife and three children. She is pregnant with another," he says as his eyes well up with tears.
The police - not a doctor - recommended he should be in the asylum for five months, but he is worried he will be forgotten.
"I don't know how I will get out of here."
Edeh Ogbonnah Bertrand managed to get out.
The 40-year-old was in the asylum for seven years.
He says he was falsely accused of stealing some bottles of malt drink by a shopkeeper, who had a police friend arrest him.
He was initially jailed in the regular prison, but was never tried.
After several months he began to protest about his imprisonment and he was moved to the asylum.
"The asylum is a kingdom of its own," he says.
"The stronger inmates make the rules. You must do what they say or they will punish you.
"They make you do things like wash the floor or the toilet or physically harm you."
Mr Bertrand was released after Prawa lobbied the state chief justice to examine the status of prisoners in Enugu Prison.
The organisation is working with families of people with mental illness trying to get them to take their relatives to psychiatric hospitals rather than to the police.
'Show them love'
The prison service itself wants to clear their facilities of civil lunatics as it says jails are already bursting at the seams with regular criminals.
The asylum was built as part of the prison during the British colonial era
Enugu Prison has a capacity of 650, but has more than 1,000 people inside.
Prisons are also filled with people who are yet to be tried for their alleged crimes.
"Civil lunatics are people that the society doesn't want to be roaming around causing problems, unfortunately they are dumped in our prisons," says Victoria Uzamaka, controller of Enugu Prison.
"We are trying to reach out to the families and to churches to get them to take care of them, show them love. In the cases we have released people have got better."
But Mr Bertrand says being rehabilitated is not an easy process.
"It's very difficult: Not having anything to do; getting used to the environment; not having any money; not having a career."
He washes cars at a shop near the Prawa office, set up so ex-prisoners can make a small living.
"Getting appointed with something to do is difficult."