Dominique Strauss-Kahn has testified to having orgies while he was managing the world financial crisis, to being “rough” with his sexual “conquests”, and to needing sex with exceptional frequency.

But no obvious evidence has emerged during a prostitution trial in northern France that Strauss-Kahn did anything illegal.

As the trial enters its third and final week, it is looking increasingly likely that the one-time presidential contender will walk away with a clean criminal record.

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Strauss-Kahn, one of 14 people on trial, is accused of aggravated pimping over a series of sex parties in France, Washington and Brussels, while he was leading the International Monetary Fund, and was married.

He insists he didn’t know the women involved were prostitutes. Two of his co-defendants say they recruited and paid the women themselves, and built a wall of silence to ensure that Strauss-Kahn wasn’t aware.

Even the prosecutor didn’t think there was enough of a case against Strauss-Kahn, and argued in 2013 against including him in the trial. Under French law, investigating judges can override prosecutors’ recommendations and send someone to trial anyway, which they did with Strauss-Kahn.

He faces up to 10 years in prison and 1.5 million euros ($A2.20 million) in fines if convicted. But Prosecutor Frederic Fevre could argue for acquittal for Strauss-Kahn during closing arguments Tuesday, focusing instead on getting convictions for other defendants accused in a large prostitution ring out of the Hotel Carlton in Lille.

During three days of surrealistic testimony by Strauss-Kahn about the sex parties, the prosecutor and his assistant remained largely silent.

Sometimes in tears, two prostitutes described “beast-like” scenes, involving sometimes brutal sex practices. One said she felt like meat in a slaughterhouse.

The testimony showed what one lawyer called the “sordid and dark reality” of the sex business. But all the prostitutes cited in the indictment, including the two testifying at the trial, said they had participated of their own accord and were never paid directly by Strauss-Kahn. They said they never told him they were paid sex workers.

Even a plaintiff’s lawyer acknowledged the case isn’t black and white.

“I have the absolute certainty that Mr Strauss-Kahn knew that there were some prostitutes in this international ring. Is that sufficient to establish a pimping offence? We will debate about that,” lawyer David Lepidi said.

Strauss-Kahn’s IMF job and presidential chances collapsed in 2011 when he was arrested in New York on accusations that he sexually assaulted a hotel maid. Those charges were later dropped and he settled out of court.

He was also accused of attempted rape of a French writer; that case was dropped because the statute of limitations had expired.

The Lille case is the first time he has been put on trial. He openly testified to extravagant sex, but said he thought the women present were “libertines” like himself.

While the line between politicians’ public and private lives has blurred somewhat in France in recent years, it remains more acceptable here for a politician to have extra-marital sexual encounters than in some other countries.

French President Francois Hollande elicited shock and criticism in the United States when caught by paparazzi visiting a lover on his motorbike, but a year later, French voters have largely moved on.

As this trial unfolds, there’s a sense that Strauss-Kahn crossed beyond even what the French tolerate from their politicians. But that doesn’t necessarily mean he will go to prison.

To prove that Strauss-Kahn is guilty, the trial has to show that Strauss-Kahn knew the women were prostitutes, and that he arranged their activities as prostitutes or profited financially from them. Prostitution is legal in France, but it’s illegal to organise a prostitution ring or profit from a prostitute’s business.

Investigating magistrates, in sending him to trial, said text messages between Strauss-Kahn and another defendant show that Strauss-Kahn was the “central pivot and principal beneficiary” of the orgies.

On occasion, he was the “instigator” and the only beneficiary, sexually serviced by several women at once, they wrote. They also said he facilitated prostitution by providing an apartment for some of the women to work.

Those arguments, however, came up only briefly at the trial.

Strauss-Kahn, who has appeared increasingly confident throughout the proceedings, may take the stand himself on Friday for a closing statement. The three-judge panel will decide on Friday when to deliver a verdict.

Chief judge Bernard Lemaire has said repeatedly – a hint of frustration in his voice – that the trial involved a lot of “feelings” expressed, suggesting there wasn’t enough hard information. He opened the trial by stressing that the court would not judge sexual activities among consenting adults.

“The court,” he said, “is not the guardian of moral order, but of the law.”

-AAP