While the stated charge under investigation is "aggravated pimping as part of an organised gang," this is really a financial investigation into whether DSK knew the women were part of an organized solicitation effort by businessmen and hotels using unlawful corporate funds. A police official is also under investigation.

He was summoned for questioning today by the Magistrates, two days early. His lawyers say they will appeal the charging decision.

DSK has said he attended the parties but did not know the women were prostitutes. Patronizing a prostitute is not illegal in France. I detailed the factual background here. Prostitution is legal in France. Profiting from prostitution (supplying them to others) is not. The police believe he was "complicit" in the acts of businessmen who supplied prostitutes or knew the businessmen were using corporate funds to pay prostitutes. DSK has denied both. The businessmen, David Roquet and Fabrice Paszkowski, back him up. One told the police:

“It is not the done thing at these kinds of sex parties to tell everyone that some of the women were being paid.”

DSK's lawyers also say the charges are politically motivated. According to one of his lawyers:

Strauss-Kahn was being pursued because of his high profile and links to France's Socialist party in the midst of a heated campaign for France's April-May presidential election.

"As a result of behaviour that is purely his own business, Mr. Strauss-Kahn has found himself -- largely because of his fame -- thrown to the wolves, by coincidence less than a month before a major election."

If he were ordered to stand trial and lost, the penalty is a maximum of 20 years in prison.

DSK was interviewed about the allegations at his request in February. He was scheduled to return to court on Wednesday, but the judges moved it up to today.