And so may begin the questioning of President Clinton on Monday, as he gives his testimony before the Whitewater grand jury about his relationship with the former White House intern.
Legal experts say Mr. Clinton should not be fooled by what will likely be general, stage-setting queries from prosecutors at the start. Soon enough, the tone will shift sharply. The questions will become more pointed and specific, the topics more graphic.
Prosecutors will be on the hunt for any inconsistencies or contradictions between his account and the evidence.
"It's the process of zeroing in," New York University law professor Stephen Gillers said. "They're going to start generally, but when they get to a bulls-eye, they may present him with contradictory documents, lab results or testimonial evidence to see if he contradicts himself."
The simplest way to do that is to make Mr. Clinton go over ground they have already covered with other witnesses or through physical evidence.
For example, prosecutors questioned Secret Service officers who might have seen the two alone, and are in possession of answering machine messages that Lewinsky alleges the president left at her home.
Before long, the questions will get highly detailed, possibly focusing on encounters that Lewinsky may have described to the grand jury, or on descriptions of sex acts. The idea is to land Mr. Clinton in what lawyers call a "perjury trap" a situation in which his story doesn't square with the evidence.
"The whole idea is basically the prosecutorial equivalent of digging a hole, putting some twigs and leaves over it and saying, `Come on, come on, come on, walk this way,"' former prosecutor Lawrence Barcella said.
Criminal defense lawyers say agreeing to testify is a risky move for Mr. Clinton because he can't know everything prosecutors have gathered.
The president, though, is no stranger to such testimony or its perils. Not only is he a lawyer, but he's already given videotaped testimony in the trials of two Whitewater figures and testified by deposition in the Paula Jones sexual harassment case.
One difference is that this time Clinton is the target of an inquiry with the highest stakes - a possible report to Congress that could lead to impeachment proceedings.
If the Whitewater trials are any indication, Independent Counsel Kenneth Starr, who is not a prosecutor by trade, won't question the president himself. In the 1996 trials, he left that to his deputies, who are career prosecutors.
In the first Whitewater testimony, Star's deputy pressed Mr. Clinton enough to elicit a momentary flash of irritation. But questions for the most part were respectful.
During his Jan. 17 deposition in the Jones case, Mr. Clinton denied sexual activity with Lewinsky. Starr is now investigating allegations of perjury and obstruction of justice.
According to legal sources, Lewinsky told the grand jury she did have a sexual relationship with Clinton and discussed with him ways to conceal it, including returning gifts he had given her.
Legal experts say Starr's prosecutors are also likely to focus on several of the president's answers to other questions in the Jones deposition, such as his denial that he made a pass at former White House worker Kathleen Willey.
They may also ask Mr. Clinton whether he was aware that his aides and lawyers had contacted potential witnesses in the Jones lawsuit, and whether he authorized that. Prosecutors are investigating whether such contacts might have involved obstruction of justice or witness tampering.
Indiana lawyer Greg Garrison, who prosecuted Mike Tyson for rape and used the boxer's inconsistent testimony to help convict him, said Mr. Clinton's best course is the truth.
"Bill Clinton will not outwit a U.S. attorney," Garrison said. "They know more about the evidence to support facts against the president than the president knows himself."
By GLEN JOHNSON