Do lawyers have a duty to control their clients during depositions? Take a look at this recent article from Law.com--
Lawyer and Client Sanctioned Over Client's Conduct, Use of 'F Word' During Deposition
A federal judge has levied sanctions of more than $29,000 on a lawyer and his client after finding that a deposition was a "spectacular failure" because of the client's constant use of vulgar language and insults and dodging or refusing to answer questions, and his lawyer's failure to rein him in.
In his 44-page opinion in GMAC Bank v. HTFC Corp., U.S. District Judge Eduardo C. Robreno found that Aaron Wider, the CEO of HTFC, engaged in "hostile, uncivil, and vulgar conduct, which persisted throughout the nearly 12 hours of deposition testimony."
In defending his actions, the lawyer representing the allegedly vulgar client said that he tried to control his client, but that his actions took place off the record. The judge's response? "[E]ven if this assertion is to be believed, [the client's] continuing misconduct indicates that whatever efforts [the lawyer] made were woefully ineffectual. In fact, [the lawyer's] meek attempts to intercede and his otherwise silent toleration of [the client's] conduct only emboldened [the client] to further flout the procedural rules."
So there you go: control your clients in depositions. If you can't, it probably means you shouldn't be representing them in the first place. I sure wouldn't.