Monica Lewinsky was recalled to explain some of the gaps and contradictions between her version of her relationship with the President and the one he had given to the grand jury three days before.
She emerged from the court- house six hours later. Her spokeswoman said that she had completed her testimony and was "looking forward to beginning the process of rebuilding her life". She said Ms Lewinsky had answered all questions "truthfully and completely" - a turn of phrase that pointedly contrasted with Mr Clinton's description of his own testimony as "truthful", a formulation which exposed gaps in his answers.
Officials had earlier confirmed that Mr Clinton had raised no objections to a sample of his DNA being supplied to the FBI laboratory that was testing a dress owned by Ms Lewinsky.
The dress, rumoured to be stained with semen, had been surrendered by Ms Lewinsky under the terms of her immunity agreement with the prosecutor's office last month. The request for a presidential DNA sample strongly suggested that scientific tests on the dress were positive (the results have been the most successfully guarded secret of the whole Lewinsky affair) and that the sample was required to establish a "match" between the stain and Mr Clinton.
Unconfirmed reports said that the sample had already been supplied by the Bethesda Naval Hospital just outside Washington, where the President's blood is stored for use in a medical emergency.
Mr Clinton's admission, under questioning on Monday, that Ms Lewinsky did - as she testified - perform oral sex on him has diminished the public shock and distaste that the DNA revelation would have provoked even a week ago. It did nothing, however, to dispel the suspicion that without the evidence of "that dress" Mr Clinton might have persisted much longer in his denials of sexual activity with Ms Lewinsky.
Until yesterday's military action, these suspicions, and the gathering impression that Mr Clinton lied in January, when he could not "recall" ever being alone with Ms Lewinsky, were leading some pollsters to forecast an imminent drop in Mr Clinton's still mostly buoyant popularity ratings. Latest polls showed that while almost 60 per cent of those asked believed he could put the Lewinsky affair behind him, almost half said that he should consider leaving office if he lied in January, and 65 per cent said he should leave if he lied to the grand jury this week.
Reports coming in from the further reaches of the US appeared to support such a trend, with some Republican candidates in this autumn's mid-term congressional elections, starting to exploit their "family values" advantage. At this stage, the trend appeared to be driven less by the politicians - who understand the risk attached to espousing moral piety - than to meet criticism of voters that their elected representatives were not showing sufficient moral outrage.
At the centre of yesterday's questioning of Ms Lewinsky were said to be presents she had received from Mr Clinton and later returned to the President's personal secretary, Betty Currie. At issue was whether Ms Lewinsky or the President had instigated their return, and why.
Mr Clinton said after his testimony on Monday that "at no time did I ask anyone to lie, to hide or destroy evidence or to take any other unlawful action", but Ms Lewinsky has indicated that the gifts were returned at his suggestion, which could support accusations that he tried to keep evidence of their relationship from the prosecutors.
What was said to have "outraged" Ms Lewinsky about Mr Clinton's admission was the inference that her relationship with him amounted to no more than "sexual servicing". She was said to have believed that the relationship was emotional as well as sexual, and had the potential to last.
Her adverse reaction was said yesterday to have compounded worries in the White House camp about the longer-term public response to Mr Clinton's admission. Some White House staff accompanying the President for his holiday on Martha's Vineyard were said to be "panicked" by the hostile political reaction to Mr Clinton's admission.