NEW YORK (AP) – A federal appeals court overturned the conviction on Monday of high-powered technology banker Frank Quattrone, granting him a new trial on charges that he obstructed a government investigation of stock offerings at the height of the dot-com boom.

The 2nd U.S. Circuit Court of Appeals in Manhattan said the jury instructions in Quattrone’s trial were erroneous.

It also ordered that the case be reassigned to another judge. Quattrone’s lawyers said the trial judge, Richard Owen, made inconsistent rulings about evidence and testimony that kept their client from getting a fair trial.

Quattrone was sentenced to 18 months in prison after he was convicted of obstruction-of-justice charges in May 2004.

Quattrone, 50, has been allowed to remain free while he appeals his conviction.

Quattrone was one of the biggest names on Wall Street during the 1990s Internet stock boom. The National Association of Securities Dealers has barred him from the securities industry for life.

In its ruling, the appeals court said Owen incorrectly instructed the jury when he said jurors did not need to find a nexus between Quattrone’s actions and pending investigations of his company.

“We cannot confidently say that if a rational jury was properly instructed, it is clear to us beyond a reasonable doubt that they would have convicted Quattrone,” the appeals court wrote in a 61-page ruling.

Quattrone was convicted of hindering a federal probe into how his bank, Credit Suisse First Boston, had allocated shares of initial public offerings of stock during the late-1990s Internet boom.

The banker, who took prominent companies like Amazon.com public during that period, was the highest-profile Wall Street figure since junk-bond pioneer Michael Milken to face a criminal conviction.

Mark Pomerantz, a lawyer for Quattrone, did not immediately return a telephone message for comment on Monday. Prosecutors had no immediate comment.

Quattrone’s lawyers argued that the jury instructions were deeply flawed. At issue was whether Quattrone actually knew that investigators were seeking the documents he sought to destroy.

The appeals court said the jury was allowed to convict Quattrone if it found that Quattrone “merely called for the destruction of documents that were within the scope of those sought by the subpoenas.”

The appeals court said such a reading of the law would mean that any defendant who urges the destruction of documents might appear to violate the law without any proof that the defendant knew the documents were the subject of a subpoena.

“Clearly, that instruction is not a correct formulation of the law,” it said. “More is required; a defendant must know that his corrupt actions are likely to affect the … proceeding.”