The lawyer for Dewey & LeBoeuf’s ex-chief financial officer, Joel Sanders—the target of intense witness testimony in a months-long trial against the firm’s top three executives—repeatedly asked jurors to question the reliability of prosecution witnesses who he said changed their stories after meeting with prosecutors.

In his closing statement, Andrew Frisch zeroed in on the firm’s ex-finance director Francis Canellas, one of seven Dewey employees who pleaded guilty under a cooperation agreement with prosecutors. Canellas testified that he and Sanders met at the end of 2008 to craft a series of accounting adjustments, some improper.