The long-running battle between Ecuadorian plaintiffs and Chevron Corp. lately has been overshadowed by harsh accusations and name calling between the big-firm lawyers in the case.

In dueling briefs filed two days apart last week, attorneys from Patton Boggs, which represents the plaintiffs, and Gibson, Dunn & Crutcher on behalf of Chevron, levied a new round of charges aimed at each other, including allegations of fraud, coercion, tortious interference and “smear tactics.”