Former high-flying investment banker Frank P. Quattrone is about to find out just how unlucky he is.

Convicted in May, Quattrone, 48, is scheduled to be sentenced on Wednesday for obstructing a federal securities investigation and attempted witness-tampering, based on a December 2000 e-mail he sent his Credit Suisse First Boston subordinates endorsing a plan to "clean up those files."

Under federal sentencing guidelines, defendants convicted of similar offenses who have similar records should get similar sentences. So Quattrone, in theory, should expect a sentence much like that of multimillionaire businesswoman Martha Stewart, who was also convicted of obstructing a securities fraud investigation that did not result in criminal charges. In June, she received a sentence of five months in prison and five months in home detention. U.S. District Judge Miriam Goldman Cedarbaum also ruled that Stewart, 63, could stay free while she appealed her conviction.

But Quattrone's fate is in the hands of a far different judge, and the former Wall Street star could get a significantly tougher sentence, lawyers and academics said.

U.S. District Judge Richard Owen has a long-standing reputation for being tough on defendants, and Quattrone's lawyers have complained repeatedly that his rulings are biased in favor of the prosecution. Even worse for Quattrone, Owen publicly disparaged the defendant's stated explanation for his actions, saying from the bench, "I've never heard anything like this before in my life."

As a result, Quattrone could be facing a sentence of 16 or even 21 months, all of it in prison, and he may have to file his appeal from behind bars, lawyers familiar with the federal sentencing guidelines said.

"It really highlights the luck of the draw. Martha Stewart drew a judge who was not likely to send her to jail for a meaningful period," said Jacob S. Frenkel, a former federal prosecutor. "Frank Quattrone drew a judge who may try to max him out under the guidelines."

Prosecutors say Quattrone sent his two-line e-mail urging several hundred subordinates to remove drafts and other documents from their initial public offering files because he had been told that a federal grand jury was investigating the way CSFB doled out hot IPO shares. Stewart was convicted in June of conspiracy, obstruction and lying to investigators on two occasions to cover up the fact that she sold ImClone Systems Inc. stock after being told the company's founder was unloading his shares.

Neither Quattrone's lawyers nor the U.S. attorney's office in Manhattan, which prosecuted the case, would comment on the upcoming sentencing. But experts in the guidelines said that Quattrone's offense, like Stewart's, generally carries a recommended sentence of 10 to 16 months, half of which must be served behind bars.

Owen could make a series of rulings, however, that would bump Quattrone's sentence well beyond Stewart's five months.

Unlike Stewart, the former banker, who earned $120 million in 2000 helping bring high-tech companies public, took the stand in his own defense twice -- his first trial ended in a hung jury in 2003; the second jury convicted him. That means Owen has the option under the guidelines of bumping the sentencing range up to 15 to 21 months if the judge finds the Los Altos, Calif., resident lied on the stand, outside lawyers said.

And if Owen really wanted to sock it to Quattrone, he could rule that a recent U.S. Supreme Court decision, Blakely v. Washington, rendered the sentencing guidelines unconstitutional and give him a longer sentence. Obstruction carries a maximum of 10 years in prison.

"The obstruction offense is one of the few white collar crimes where many people believe the guidelines may not be strong enough," said Washington defense attorney Kirby D. Behre, who has written a book on the sentencing process. "Is 16 months really enough of a sentence where you've attempted to scuttle a government investigation?"

Still, Behre and other sentencing experts agree that the worst-case scenario is unlikely, lawyers said. The Supreme Court isn't scheduled to rule until this fall on how Blakely affects the guidelines. The U.S. Court of Appeals for the 2nd Circuit, which will get Quattrone's case on appeal, said the guidelines remain in effect at least until the high court rules. The Blakely case also casts some doubt on whether Owen can give Quattrone extra time if he finds he lies on the stand, said Indiana University law professor Frank Bowman.

As a result, most lawyers said they believe Quattrone is likely to get a sentence at the top of the original 10-to-16-month range and be required to serve all of it in prison.

"The way the judge can make the sentence less to a challenge is to say, 'I think that he lied, but I'm not going to bump him up.' If you really don't like him, why would you give him a legitimate appeal issue?" said Barry Boss, a Washington defense lawyer. "You can say whatever you want about Martha Stewart, but the judge gave her a huge break."