A judge declared a mistrial Friday in a Chicago Roundup case after one of Monsanto’s attorneys mentioned during a cross-examination that the plaintiff had once been charged with a criminal offense.

Associate Judge Daniel Trevino of the Cook County Circuit Court ruled that the lawyer’s line of questioning constituted “serious misconduct” and cautioned the defense against “any further conduct that could result in sanction or a contempt finding,” according to a transcript from the proceeding. The case had been in its fourth week of trial.