A federal jury returned a verdict against a Cook County assistant public defender who alleges he was denied a promotion in favor of less qualified applicants.The jury in U.S. District Judge John Robert Blakey’s courtroom found Tuesday that Patrick J. White had not proven he was a victim of age, race and sex discrimination when he was not promoted.Also on Tuesday, Blakey found White had not proven his claim that policies and practices followed by the Public Defender’s Office had a disparate impact on him because …