A retired Massachusetts lawyer has been found guilty of involvement in a major art theft that extends back three decades.

On August 18, a US District Court jury in Boston found Robert M. Mardirosian, 74, guilty of possession of goods that had crossed a United States boundary that he knew to have been stolen.

The goods in question were seven paintings stolen in 1978 from the Stockbridge, Massachusetts home of collector Michael Bakwin. The largest burglary from a private residence in Massachussetts history included Paul Cezanne’s Bouilloire et fruits, Portrait d’une Jeune Fille and Portrait d’un Jeune Homme by Chaim Soutine, Woman Seated and Boy by Jean Jansen, Flowers by Maurice de Vlaminck and Maison Rouge by Maurice Utrillo.

Mardirosian practiced law for many years in Massachusetts and once represented David Colvin, the alleged thief, who was never convicted due to insufficient evidence and subsequently murdered in 1979 over a gambling debt.

Mardirosian claimed Colvin left the paintings in a loft in his law office in Watertown. He kept possession of them and in 1998 embarked on an international tour taking them to Swiss banks and London auction houses, partly under the cover of a company registered in Panama, Erie International Trading Company, which he created to sell the works.

In 1999, underwriters Lloyd’s of London contacted the Art Loss Register (ALR) after being asked to insure the movement of the works from Russia to London for valuation and sale. In cooperation with the FBI, the ALR negotiated the return of the Cezanne in return for relinquishing title to the other six works. The Cezanne was then sold on behalf of Mr Bakwin in the Impressionist and Modern Art sale at Sotheby’s in December 1999 for £18m.

In 2005, four more of the works were consigned to Sotheby’s London through an intermediary from Erie International, Paul Palanjian. Mr Bakwin and the ALR argued successfully in court that the original agreement relinquishing title was void because it had been entered into under duress and was against public policy, and the works were returned to Mr Bakwin.

The final two paintings had remained in Switzerland and are now in the hands of the authorities in Boston.

The criminal trial focused on whether Mardirosian possessed any of the paintings in the five years prior to his indictment in March 2007, as the statute of limitations for other offences had passed.

One of Mardirosian’s lawyers, Jeanne M Kempthorne, told jurors in her closing arguments that she was not defending her client’s failure to notify Bakwin for decades that he had possession of the paintings. She said the key issue was the legal status of the paintings after 2002, at which point Mardirosian believed he legitimately owned them because of the 1999 agreement.

Chief US District Court Judge Mark L Wolf ordered Mardirosia to be held in custody pending his sentencing on November 18, when he faces a maximum of ten years in a federal prison.