The most burning question - did you kill Stephen Lawrence? - has been ruled out by two High Court judges, who said it was outside the inquiry's terms of reference. But the appearance of the suspects before the public inquiry in Elephant and Castle will provide a dramatic climax to three months of hearings into Stephen's death.
Legal argument about the scope of the questioning has been raging for two weeks, and the five will face tough interrogation, particularly from Michael Mansfield QC, counsel for the family, on vital matters related to the murder, such as their movements on the night. They will also be asked about what happened when they were arrested and interviewed by police.
Feelings in the chamber are expected to run high, and police officers will be stationed around the room to head off any violent confrontations.
All five have at various times been charged with killing Stephen, who was stabbed to death by a white gang in a racially-motivated attack as he waited for a bus home in Eltham, south-east London, five years ago. The case came to court in 1996 as the result of a private prosecution mounted by the Lawrence family. Neil Acourt, 22, Gary Dobson, 22, and Luke Knight, 20, were acquitted after the trial judge ruled out identification evidence.
Charges were dropped at the committal stage against the other two, Jamie Acourt, 21, and David Norris, 21, who could in theory still be tried by a jury. However, evidence that they give to the public inquiry cannot be used against them in a criminal prosecution.
Another likely area of questioning today, when David Norris takes the stand, is allegations of a corrupt link between the murder squad and his father, Clifford, a local criminal.
They will also be asked whether they are racists, whether they have any black friends and what their views are on ethnic minorities - despite an objection during legal argument last week by one of their barristers that such questions were designed to "rub their noses" over a police surveillance video which captured them fantasising about torturing black people.
Sir William Macpherson of Cluny, the inquiry chairman, has the difficult job of adjudicating on the questions that may be asked by Mr Mansfield and Edmund Lawson QC, counsel to the inquiry, as well as lawyers for Duwayne Brooks, Stephen's friend, who was with him when he was killed, and for the various ranks of police officers. The three barristers funded by the inquiry to represent the men are likely to raise numerous objections.
The High Court, which dismissed a last-minute attempt by the five to avoid answering their summonses, ruled that since the inquiry is concerned with the conduct of the police investigation, it would be wrong to ask them whether they are guilty or innocent of the murder.
Sir William has said that he will not permit them to be asked whether there is any truth in other allegations against them, including allegations of involvement in previous violent attacks in the area.
Among those watching the men give evidence will be Stephen's parents, Neville and Doreen Lawrence, who are convinced that they are his killers.
Their appearance before the tribunal is a security nightmare for police and inquiry staff, who have to chaperone them inside the building while marshalling the crowds of would-be spectators competing for limited seats.
A tight security operation will swing into action this morning. Large numbers of police officers will be stationed outside, where demonstrations are expected by anti-racist groups. There are fears that the event may also attract members of neo-Nazi organisations.
People who attend will have to pass through recently-installed metal detectors and have their bags searched. Inside the inquiry chamber marshals organised by the Stephen Lawrence Family Campaign will help police to keep order.
The testimony of the five men follows nearly 50 days of evidence by the police officers who failed to bring Stephen's killers to justice. The inquiry has heard that the Acourts, Mr Dobson, Mr Knight and Mr Norris were named by dozens of informants in the local community in the first 48 hours after the murder. No arrests, however, were made for two weeks.
Senior detectives have admitted that they made numerous mistakes in the initial stages of the investigation. Belongings were removed in dustbin bags from the Acourts' house under the noses of a police surveillance team. Arresting officers failed to search the suspects' homes properly.
Now the tribunal is hoping for some answers from the men themselves, and the laws governing public inquiries require them to respond to all questions put to them. If they refuse, they could be fined or jailed for up to six months.
Sir William reminded lawyers last week of the High Court's ruling that their appearance at the inquiry should not be turned into a criminal trial. But he agreed with Mr Mansfield that the men must not be allowed to use it as an opportunity to "assert their innocence with impunity".
Sir William's task involved "skating on the thinnest of ice", he said. "I readily understand that the Lawrence family's position remains that all five are responsible for Stephen's death.One can understand and sympathise with their position. But everyone must realise that fairness must prevail, whatever one thinks of these men."
The case so far
These have been the key days of evidence in the inquiry so far:
24 March: Edmund Lawson, QC, counsel to the inquiry, opens the hearings with a statement describing the police investigation as "seriously flawed".
30 March: In a statement read out to the inquiry, Neville Lawrence says he was told by a visitor to his house that the suspects were seen washing blood off themselves on the night of the murder.
8 May: Michael Mansfield QC, counsel for the family, alleges that there was a corrupt link between a police officer and Clifford Norris, a notorious criminal and father of one of the five suspects.
13 May: Ian Crampton, who led the investigation during the first weekend, admits that he should have made arrests within 48 hours.
14 May: The suspects announce that they plan to seek leave to apply for judicial review of the decision to call them to give evidence at the inquiry.
15 May: Duwayne Brooks (right), who was with Stephen when he was murdered, tells the inquiry: "Racist thugs killed Steve and shattered my life."
27 May: Brian Weeden (right), head of the murder squad for 14 months, admits that until recently he did not understand the legal grounds on which police officers can make arrests.
11 June: Neville and Doreen Lawrence give evidence in person. Mrs Lawrence interrupts questioning by a barrister for the Metropolitan Police, asking: "Am I on trial?"
12 June: The High Court grants the suspects leave to apply for judicial review.
15 June: The inquiry watches a videotape recorded by a secret police camera hidden in the flat of one of the suspects, which shows them brandishing knives and expressing violent racist views.
17 June: Speaking through a high-ranking Metropolitan Police officer, Sir Paul Condon, the Commissioner, apologises to the Lawrence family for the first time for the incompetence of the investigation.
18 June: Lord Justice Simon Brown dismisses the judicial review application, but says that the five may not be asked whether they killed Stephen.Reuse content