An accounting expert testified in federal court on Friday that Manhattan’s Knoedler Gallery sold fake art from Long Island fraudster Glafira Rosales for $69.7 million and cleared gross profits of $43.1 million over a 17-year period.

The expert, Roger Siefert, testifying in Manhattan in a lawsuit brought by a couple that bought a bogus Mark Rothko painting for $8.3 million, also said Knoedler president Ann Freedman earned “profit-sharing” payments of $10 million from 1994 to 2011 while peddling the phony works.

The lawsuit by Sotheby’s chairman, Domenic de Sole, is the first civil damages trial stemming from the fraud by Rosales, of Sands Point, who pleaded guilty in 2013 to selling purported works by Rothko, Jackson Pollack and other famous artists that had been forged.

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Siefert, a forensic accountant who analyzed the books of Knoedler, once New York City’s most prestigious gallery, testified that if not for the sale of the fake works it got from Rosales, the gallery would have been in the red for the 17-year period.

Freedman and Knoedler claim they were duped by Rosales, just like the buyers they sold to and other experts. Freedman is expected to testify in the case next week. Rosales has not been sentenced.