The problem with the exact statement you use being a "lie" is that it is opinion that it is impossible to enter the mind of the attorney and know if he did or did not believe his statement, irrespective of the ridiculousness of it. And because of attorney/client privilege, it is unlikely you would ever know exactly what he does or does not know about about his client's true actions. So, while an attorney may not lie, functionally proving they did is virtually impossible for a statement like that.