Leading article: Innocent until proven guilty; that applies to the maid, too

When the head of the International Monetary Fund was arrested in New York on attempted rape charges, the reverberations were felt far beyond North America and brought together wildly disparate worlds.

A major international financial institution was decapitated at a crucial juncture in the euro crisis. The French Socialist Party's hopes of recapturing the presidency in 2012 were dashed, and a particularly ruthless side of the US penal system – the "perp" walk, in which a handcuffed suspect is paraded in public – was exposed. And all because of another, far more admirable, aspect of US justice: the right of a low-paid immigrant maid in a luxury New York hotel to invoke the law in her defence against a very rich and powerful man.

Seven weeks later, and the Dominique Strauss-Kahn affair has produced new shocks, no less shattering than the first. The IMF may be back on an even keel after the smooth appointment of its first female managing director – another French citizen, Christine Lagarde. But almost every other new certainty has been overturned. The prosecution has admitted that it is now much less sure of its case. Mr Strauss-Kahn has been released from his most onerous bail conditions. Doubt is being cast on the credibility of the maid, whose life in the US may not have been all it seems. And across the Atlantic, French Socialists are back in turmoil, asking themselves whether Mr Strauss-Kahn might not be their presidential saviour after all.

In this roller-coaster of a case, there are two aspects that may, in the end, bring beneficial change to two quite different systems of power. And there is one – central – aspect that will not, or should not, change anything at all.

First, the United States. The extent of international distaste for a judicial system that seems almost to delight in humiliating suspected felons has been brought home to Americans in no uncertain way. That the head of the IMF could be brought to such depths of indignity as he was when he was first arrested and charged not only sent the positive message that everyone is equal before the law, but showed how the very process of arrest, New York style, can place defendants at a disadvantage. Legally, they may be innocent until proven guilty, but they are made to appear guilty at the start. If this is true for such an eminent person as Mr Strauss-Kahn, what hope can there be for the less suave and less confident majority?

Second, to France. After popular indignation about insults to the national honour had died down, the charges against Mr Strauss-Kahn precipitated a discussion of sexual harassment in France – the first such open airing of an affliction from which the country had liked to believe it was exempt. Since then, a junior minister has resigned and been arrested over sexual assault allegations, while women's groups say the reporting of incidents has increased several times over. Sexual harassment will probably not be dismissed as a purely Anglo-Saxon preoccupation again.

As for what will, or should, stay the same. Mr Strauss-Kahn's accuser, the Guinean-born maid, has gone in seven short weeks from being depicted as a wronged woman with the courage to challenge a rich assailant to a professional fraudster and prostitute. Any court case is likely to hinge on her credibility. Yet the charges must stand or fall on their own merits. That the maid – and we have yet to hear her response to any of the attempts to blacken her character – may have lied her way into the US; that she may have used a rape claim as an alibi for her asylum application; that she may have combined chamber-maiding with prostitution do not, of themselves, annul her accusations against Mr Strauss-Kahn. Attempted rape remains attempted rape, however powerful the perpetrator, and however lowly and otherwise discredited the victim.