But what Starr can do as a prosecutor and what he ought to do as a public servant differ.
What will happen if Starr reveals a positive result to Clinton? He probably destroys his own case. No matter how much Clinton might want to brazen it out, advance warning from Starr would compel the president to admit and apologize. So Clinton wouldn't perjure himself and, as I argued Sunday, an apology is likely to kill the appetite for any impeachment hearings (over obstruction, Whitewater, Filegate, etc.). Starr's criminal case goes up in smoke.
Whether Starr gives it away depends on what kind of prosecutor he is. If he wants to expose criminal behavior by the president and punish it no matter what--if, in short, he is the vindictive avenger Clinton's defenders say he is--Starr will sacrifice no advantage. He will blindside the president with test results if that will build a stronger case. But if he's a prosecutor who wants to turn up the truth as much as to get his target, then Starr will give it away.
"The decent and sensitive thing to do is tell the president. There is no advantage whatsoever to getting the president to lie before the grand jury," says former Deputy Attorney General Philip Heymann. "[Starr should] not put himself in the position of having called the president and inviting him to lie unnecessarily."
Or, as Washington, D.C., criminal lawyer Robert Luskin puts it, "You just don't play a game of chicken like that with the president of the United States."
There are strong public policy reasons for Starr to give the results away. Do we really want the president's career to rise or fall based on prosecutorial cleverness in a secret grand jury proceeding? Telling Clinton the results makes it more likely he'll go public, and that makes it more likely Flytrap will be played out in the open rather than in private legal proceedings. And the public political realm is where Flytrap belongs.
One of Starr's obligations as a prosecutor is to protect the honorable institutions of government, and one of those institutions is (believe it or not) the dignity of the presidency. That dignity has been much squandered by Clinton, but this is a chance for Starr to protect what remains. Starr protects the presidency by exposing criminal behavior by the president. But he can also protect the presidency by preventing more criminal behavior. Not telling the president of a positive DNA result may induce Clinton--admittedly because of his own hubris--to lie, to trap himself, to damage the office of the presidency even more. Telling the president lets Clinton avoid committing a new crime.
The person who would benefit most of all by telling is Starr himself. He has been demonized as the prosecutor who is destroying the president over sex. He can become the prosecutor who let the president save himself.