A Portland native and former Cheverus High School trustee who had been sentenced to more than six years in prison for insider trading was exonerated Wednesday when a federal appeals court overturned his conviction and that of a colleague.

In a decision that experts say could have broad implications for securities law, the U.S. Court of Appeals for the Second Circuit in New York ruled that prosecutors failed to prove that two New York hedge-fund managers, including 1991 Cheverus graduate and recent trustee Anthony Chiasson, knew they were trading on insider information or that insiders received payment in exchange for that information.

Chiasson, 41, the former manager and co-founder of Level Global Investors LP, was convicted by a jury in 2012 of securities fraud for involvement in a high-profile insider-trading scheme that illegally netted around $70 million. Sentenced last year to six years in prison and fined $5 million, he had been granted bail pending his appeal.

The decision handed down Wednesday also overturned the conviction of Todd Newman, portfolio manager for Diamondback Capital Management LLC, who had been sentenced to more than four years in prison.

Newman and Chiasson were among seven analysts and fund mangers arrested in 2012 on charges stemming from a scheme that involved trading on inside tips from employees at Dell Inc. and Nvidia Corp., in 2008 and 2009. They were the only two who did not plead guilty to fraud.

“Newman and Chiasson were several steps removed from the corporate insiders and there was no evidence that either was aware of the source of the inside information,” the decision said.

The ruling set a new standard for insider-trading convictions and could affect the future of securities enforcement, as well as other cases in the Manhattan U.S. Attorney’s recent crackdown that are still pending, according to reports Wednesday by national news outlets, including Forbes and The New York Times.

U.S. Attorney Preet Bharara said in a statement Wednesday that the decision “will limit the ability to prosecute people who trade on leaked inside information,” but that it “affects only a subset of our recent cases.”

Bharara’s office is assessing the decision and considering options for further appeal.

But for Chiasson, the decision marked the end of a long ordeal that included intense media attention and the prospect of missing out on his two young children’s formative years.

“Today’s decision is a resounding victory for the rule of the law and for Anthony Chiasson personally,” his lawyer, Gregory Morvillo, said in a statement Wednesday. “Mr. Chiasson has always conducted himself according to the highest ethical and professional standards in service to many of the world’s leading hedge fund investors who were his clients for years. He is deeply gratified that the decision issued today unequivocally reestablishes his innocence under the law – consistent with what Anthony has steadfastly maintained for the duration of this ordeal. He thanks his family, friends, former clients and colleagues for their unwavering support.”

Chiasson grew up the youngest of four children raised in Portland by Lucille Chiasson. His parents divorced when he was 6. He served as an altar boy, attended St. Joseph’s parochial school and helped his grandparents take care of several properties they owned, according to court documents.

As a student at Cheverus, he was president of the National Honor Society and graduated seventh in his class. He went on to attend Babson College in Massachusetts, where he served on the judicial board, graduated summa cum laude and was named “top senior” for his academic achievement and contributions to the college community.

Chiasson was a member of Cheverus’ board of trustees from 2009 until his arrest in 2012, when he resigned. The youngest member of the school’s board by 20 years, he came to Maine three times a year to attend meetings and helped create a five-year plan to stabilize the Jesuit school’s finances when its closure was under consideration, court documents said.

He also served on Babson’s board of trustees and set up a scholarship program for students at the college who came from Maine and needed financial aid, contributing $20,000 per student.

Annual giving reports indicated that Chiasson donated at least $10,000 a year to Cheverus in the two years before his arrest. Cheverus officials previously have refused to disclose his total donations to the school. Calls to the high school’s staff and board chairman were not returned Wednesday.

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