Abuja - In June 150 prisoners escaped from Enugu state prison in southeastern Nigeria, beating wardens and raping female prisoners before they fled.

A few weeks earlier eight inmates reportedly were killed in another jailbreak, at Agodi prison in Ibadan in the southwest.

Escape may appear to some prisoners to be the only way out, given that some two-thirds of Nigeria's prisoners have been detained without trial, according to a report by the Centre for Social and Legal Studies (CSLS) in Abuja, which calls on the government to pass criminal justice reform legislation immediately.

The May report, 'Justice sector reform and human rights in Nigeria', says in the Kuje prison in the capital Abuja 85 percent of the 622 prisoners have not been tried. A 2008 Amnesty International report estimated the overall number of detainees without trials at 65 percent.

The researchers saw prisoners who have been awaiting trial for nine years.Why.

All stages of the criminal justice system contribute to delays, said Yemi Akinseye George, senior lecturer in legal studies at the University of Ibadan and co-author of the report.

Police often arrest and detain people on "holding charges" while they collect evidence, George said. "That is wrong. It is illegal...It is against the constitution."

Bail conditions are often impossible to meet, said Adekunle Ojo, a human rights lawyer and vice president of the Nigeria Bar Association.

With few government-subsidized legal aid programmes, prisoners often cannot afford a lawyer, said Professor George, leaving courts in a bind. "People cannot afford assistance, but courts cannot release them when there are no lawyers to take up their cases."

In some cases, ineptitude has led to the loss of hundreds of files, the report says.

When a case does go to court, witnesses - with no official protection scheme in place - are often too frightened to give evidence, leaving cases hanging, in some cases for years.

With no trial, many prisoners end up spending more time detained than they would have under a conviction, according to human rights lawyer Ojo. Minor offences such as petty theft or traffic offences incur a maximum six-month sentence in Nigeria.

Justice Minister Michael Aondoakaa says the problem lies in the structure of the criminal justice system, whereby the federal government owns and operates prisons but state courts sentence prisoners.