WASHINGTON -- David Nathanson, a young Boston public defender, had waited his entire legal career for this moment.
After Rutgers Law School and then defending indigent defendants in lesser cases, the 33-year-old was standing before the Supreme Court, an experience few lawyers are ever privileged to have.
He walked into a legal buzzsaw. Here was Justice Sandra Day O'Connor, the court's famous swing voter and reputedly the most powerful woman in America, pressing him to answer a complicated question.
As Nathanson launched into a complicated answer, the 74-year-old O'Connor leaned forward and interrupted. ''Just answer the question for once," she snapped.
That's the way it went for Nathanson yesterday, as he struggled to persuade the court that once a judge acquits a defendant of a charge, even if it's a mistake, that decision is irreversible. Reinstating the charge, he argued, violates a defendant's constitutional protection against double jeopardy, being prosecuted twice for the same offense.
For Nathanson's client, Melvin Smith, winning the case would only marginally improve his chance of parole, because it would not erase two other convictions related to a shooting in Roxbury Crossing in 1996.
At his trial, Smith should have been home-free on the charge of unlawful possession of a firearm after Superior Court Judge Elizabeth Donovan granted a midtrial motion to find him not guilty, Nathanson argued. When she later realized that she had made a mistake and reinstated the charge, it should have been too late, the lawyer contended.
Smith appealed the case unsuccessfully in state courts, but he managed to persuade the Supreme Court to hear it.
No lawyer from the Massachusetts public defender's office had ever taken a case all the way to the Supreme Court. For weeks, his colleagues had been helping him prepare in mock oral arguments.
Nathanson walked into the courtroom with one point to make: An acquittal is an acquittal.
But the justices had numerous concerns: A judge can reconsider a midtrial ruling in a civil case, so why not in a criminal one? What if a judge makes a clerical mistake? What if a jury doesn't hear about the acquittal before it's corrected?
Perhaps Nathanson's most tortured encounter was a prolonged exchange with Justice Stephen Breyer, who wanted Nathanson to articulate a simple rule for when an acquittal is final. Breyer kept cutting him off as he launched into a complex and conditional answer. Finally, Justice Antonin Scalia answered the question himself.
''Once it's final under state procedure -- and there's no clerical error, leaving that aside -- it's final," Scalia said. ''If there's a mistake, too bad."
Breyer replied, to laughter: ''Excellent. That was an excellent answer."
Still, Justice David Souter had picked up on Nathanson's point, asking, ''Why can't we have a rule [for judges] that you better be serious, you had better not [acquit a defendant] in a snap judgement, because once you do it, it sticks, so think it over?"
The justices are expected to decide on the case before the current term ends in June.
Nathanson's opposing counsel, Cathryn Neaves, had also never appeared before the Supreme Court before, but she was much more seasoned. As chief of the criminal bureau's appellate division in the Massachusetts attorney general's office, she had appeared numerous times before state and federal appeals courts and the state Supreme Judicial Court.
Afterward, Nathanson looked both relieved and exhilarated. When a reporter mentioned that it was Nathanson's first appearance before the Supreme Court, he joked, ''Gee, you could tell?"
Still, when asked how he thought it would turn out, he spoke like the newly minted veteran he now was: ''I may not be very experienced in arguing before the Supreme Court, but I know enough not to make a prediction."