Now that Monica Lewinsky has had her day in court, as it were, President Clinton faces decisions that could decide the fate of his Presidency when he testifies to the grand jury on August 17th.

What Ms Lewinsky told the jury over about six hours on Friday is supposed to be secret, but it did not take long for a number of media outlets to report confidently that she claimed to have had more than a dozen sexual encounters with the President in the small study off the Oval Office over a period of 18 months.

This was no surprise. From the time it was announced last week that Ms Lewinsky would testify in exchange for immunity, it was assumed that she would tell the grand jury under oath that she had a sexual relationship with Mr Clinton, thus contradicting earlier sworn testimony by both of them.

The whole point of the immunity deal was that she could not be charged with perjury for going back on her sworn statement last January to lawyers representing Ms Paula Jones in her action - now dismissed - against Mr Clinton for alleged sexual harassment. Ms Lewinsky's 20 hours of taped conversations with former colleague Linda Tripp are apparently full of references to a sexual affair with the President.

On Monday week it will be the President's turn to either stick by his categorical denials last January of ever having had sex with Ms Lewinsky or else retract and confirm her latest story. But unlike her, he does not have immunity and is in fact a target of independent counsel Kenneth Starr, who is preparing a report for Congress which could lead to his impeachment. Apart from the President, his wife Hillary and his personal lawyers, no one knows what he plans to do when he gives his testimony on a TV circuit to the grand jury from the White House. He said last week at a public appearance that he would testify "completely and truthfully". White House aides say they have no reason to doubt the truth of his earlier testimony.

The fact that last week the President chose not to repeat his denial of sexual relations with Ms Lewinsky may or may not be significant. But if he maintains this denial, he will be in direct conflict with her testimony. Or will he?

Ms Lewinsky has apparently also told the grand jury that the kind of sex they had together was not regarded by the President as constituting "sexual relations" and so he had "deniability" if needed. However, before he made his sworn denial last January 17th, the lawyers for Ms Jones first defined in detail for him what they meant by sexual relations and it certainly included what Ms Lewinsky is now claiming took place.

This would mean that it could be the President's word against that of Ms Lewinsky - and she is now an admitted perjurer. Defenders of the President also point to something she has said on the Tripp tapes: "I was brought up with lies all the time . . . That's how you get along . . . I have lied my entire life."

A crucial piece of material evidence could yet be the dress belonging to Ms Lewinsky which is being examined in the FBI laboratory for traces of genetic material which she alleges is proof of sexual relations with Mr Clinton. A positive test would be one which confirmed there was such material but of unknown origin at this stage, and there have been "insider" claims that the tests have been positive.

The next step would be to see if Mr Clinton can give a matching DNA sample from his blood or if he would be prepared to give a sample at all.

While there has been a huge concentration on the sex part of this extraordinary tale, a more serious aspect for the President is whether he can be accused of obstruction of justice and/or suborning perjury. Thus Mr Starr is also collecting evidence which might show that the President wilfully intended to prevent the lawyers for Paula Jones from getting truthful testimony.

This gets into complex legal areas, but lawyers put it this way. If the President and Ms Lewinsky just discussed how they could hide a sexual relationship from the outside world, that would not be seen as illegal or corrupt behaviour. But if what was discussed was ways to prevent the lawyers in the Jones civil action from getting truthful testimony following subpoenas to the President and Ms Lewinsky, that could be obstruction of justice.

If the President urged Ms Lewinsky to lie in her testimony, that would be subornation of perjury. It appears that Ms Lewinsky in her testimony stops short of putting the President in that position. According to the Washington Post, they developed "cover stories" but he did not tell her to lie.

This does not mean that Mr Starr will not try to build up a case for obstruction of justice by the President through what happened to the gifts he gave Ms Lewinsky and the efforts to find her a job away from Washington. It is argued that, given the power and prestige of the presidency, a hint from Mr Clinton to a young intern could be seen as a virtual order.

When all is said and done and the lawyers have had their say, it is only the Congress of the United States which can remove the President from office. Constitutional lawyers mostly agree that Mr Starr has not the power to indict the President on a criminal charge of, say, perjury.

But if Mr Starr sends a report to the House of Representatives making a persuasive case that the President obstructed justice or committed perjury before the grand jury, the impeachment process would be triggered. The House would hold hearings, probably calling Ms Lewinsky and others who have been before the grand jury. This time there would be no grand jury secrecy.

This is why even some supporters of President Clinton have been advising him to go down the mea culpa path and tell the grand jury and then the US public that he lied last January to protect his family and Ms Lewinsky. This way, it is argued, even a Republican Congress would have no stomach for the impeachment road and a chastened Clinton would serve out his second term.

Of course, we do not know what President Clinton will say to the grand jury. He can stick to his denials and in effect call Ms Lewinsky a perjurer, but put himself at risk of being accused of committing perjury himself a second time.

It may come down to the question of what "sexual relations" are, and what is or is not on the dress. A lot of Americans feel that that is down a lot further than the US presidency should ever have been dragged.