The question of how far lawyers can go in providing clients the strongest possible defense underlies a rare trial coming to an end in Chicago.

Closing arguments are planned for Thursday in the federal bench trial of Beau Brindley. The 37-year-old faces obstruction of justice, perjury and other charges after prosecutors say he instructed clients and witnesses about how to lie to judges and juries.

But on the stand this week, Brindley insisted his overriding message to clients has always been to tell the "absolute truth."

A leading authority on legal ethics says most lawyers eschew the kind of question-and-answer scripts Brindley is accused of using. But Stephen Gillers also concedes "the ethics of witness preparation can be murky."

Trials like Brindley's are rare, partially due to attorney-client privilege.