A federal appeals court has affirmed a former Nixon Peabody partner’s prison term of seven years, clarifying for the first time that lawyers convicted of covering up their clients’ crimes could face additional enhancements to their sentences.

David Tamman was convicted in a 2012 bench trial of back-dating securities documents for a former client, John Farahi, founder of Newpoint Financial Services Inc. in Beverly Hills, Calif., which federal prosecutors claimed was a $22 million Ponzi scheme. He is serving his sentence at a federal prison in Lompoc, Calif.