US-led international forces in Iraq are currently holding thousands of Iraqi people suspected of involvement in the violent campaign against the Iraqi government and the occupying forces.
But some detainees complain of arbitrary detention and abusive treatment.
Peggy Gish, 62, is an American woman who has spent 13 months over the past two years logging the cases of Iraqi detainees with the ecumenical humanitarian group Christian Peacemaker Teams.
She told the BBC News website about her experiences.
We were not allowed to go into prisons, so our contact was with the families of detainees and freed detainees. We got very careful testimonies.
We were hearing some of the same stories from people all over Iraq, so we were fairly certain what we were hearing was accurate.
Peggy Gish, left, logging the cases of detainees
We heard about very violent house raids in the middle of the night, in which US soldiers would storm in, and if the men did not get down immediately, they would knock them down and beat them.
Then their house would be ransacked, often with property damage. Many would report that at the end of that time jewellery and money would be missing. Then the men of the household would be taken away.
We heard the same kind of details over and over from all around the country.
We talked to the US military about those house raids, and though they denied the soldiers would take money or gold, they did not deny that they would go in with 25 seconds of absolute fury and try to bring the people into submission very quickly.
Then we began to hear stories of a very violent interrogation process. Men would report being kept in very painful positions for hours at a time, being deprived of sleep and water and food, some kept out in the hot summer sun for hours.
We also heard about sexual abuse and beatings when they were being questioned. If they did not give information about an explosion or something they would be knocked down, kicked in the groin, and hurt in other ways.
6,700 security detainees held by multinational forces in Iraq (Source: MNF)
10 major detention facilities in Iraq (source: Human Rights Watch, May 2004)
Most detainees held in Abu Ghraib prison in Baghdad and Camp Bucca in Um Qasr (source: Coalition Provisional Authority document obtained by CPT in May 2004)
Many detainees first held in temporary facilities for initial or secondary interrogation (source: HRW)
Iraqi families also believe some detainees held outside Iraq in facilities in Qatar, Kuwait and Germany (source: CPT)
These men were held in Abu Ghraib and in prisons across the country. We think it is better since the Abu Ghraib scandal - we are not hearing the stories of overt sexual abuse - but people are still being humiliated and there is still a lot of physical brutality.
Many men are held because they happened to be on the street, even blocks away, from an explosion. The US military would round up hundreds of men in the area to try to find the few that caused the blast.
In fact, we came to the conclusion that 80% to 90% of the prisoners had never been involved in any violent action. This is an estimate that tallies with the estimates of other groups such as Amnesty International and Human Rights Watch.
A common reason for men to be detained is because an informant in the neighbourhood has given their name to US military and claimed that they are part of the resistance.
Informants get money for each name they give, and many people have told us that informants use the system to revenge personal grudges.
They say it is rather like life under Saddam Hussein. Many Iraqis use an Arabic expression, "Same donkey, different saddle".
Back in December 2003, when we completed our first report, we sent copies to the US civilian and military authorities in Iraq.
We were received well, and we believe our reports helped make it difficult to cover up the abuses. But we are frustrated that [reforms to detention techniques] have not gone any further despite the outrage.
Abuse reported by detainees at Abu Ghraib, Camp Bucca and Baghdad International Airport (BIAP) detention facility, and initial intake facilities
Improvements since April 2004 but reports of abuse continue
Only a small proportion of detainees face criminal charges; remainder are in legal limbo
Difficult to find information on detainees or arrange visits, though situation improved
Final fate of detainees still in hands of Multinational Forces
Property taken in house raids not returned and no receipt given
Detainees report overcrowding, lack of medical facilities, poor food and water in detention facilities, but improvements reported
In general, since Saddam Hussein was overthrown, people do have more freedom of speech, more freedom of movement, and wages are a little higher, so there are some positives.
But in many ways things have got worse - there is less electricity and water, unemployment is at 50% or 60%, there is much more danger. People are feeling very discouraged and fearful.
And in fact, people feel like it is less safe where there are multinational troops, because of the combat. In fact, the last time I was there I started hearing people say the primary source of the violence was the US presence.
People were saying: "We think the US needs to leave right away, even if there is a civil war or a power grab - it couldn't be much worse than it is now. At least we will be able to handle the situation ourselves."
There are still a few people that want the US to stay, but they're a very small minority now.
Interview by Becky Branford