Despite its greater pervasiveness, however, soft-core perjury has generated considerably less discussion and debate than hard-core perjury has. There are reasons for this, but they are not good ones. Indeed, we might summarize the matter this way: Lawyers tend to dismiss the soft-core perjury problem because they do not see it as a problem. They do not see it as an ethical problem, and they do not see it as a practical problem. They are wrong on both counts.
The idea that soft-core perjury poses no ethical problem comes from the view that the lawyer's dilemma-or trilemma, if you will-arises only ifhe or she "knows" the client is committing perjury. In other words, soft-core perjury isn't ethically troublesome because, well, it isn't hard-core perjury. What we don't know can't hurt us, and we needn't trouble ourselves with the fact that it may still hurt the integrity of the justice system.
Niehoff, Leonard. "Soft-Core Perjury." Litigation Journal 36, no. 3 (2010): 8-12