Ignorance of the law may not be an excuse, but “I didn’t know” is becoming a popular defense among public officials and others who are forced to respond to allegations of misconduct by themselves or those who work for them.

Whether it’s athletic coaches, corporate executives or elected officials, the “I don’t know” defense seems to be a common refrain. Former President Clinton may have started the ball rolling with his repeated claims not to recall certain events of his presidency during impeachment proceedings against him. Since then, people in various fields have used ignorance of events as a shield against responsibility or guilt. Even those who are willing to acknowledge that they, as the bosses, ultimately are responsible, seek to deflect blame by pleading ignorance.

Kenneth Lay, former chief executive of Enron Corp., did it when he pleaded not guilty to 11 counts of securities fraud, wire fraud, and false and misleading statements. In a press conference after appearing in court, Lay acknowledged that he, as chairman was responsible for the company’s collapse, but added, “that does not mean I know everything that went on at Enron.”

College coaches, including two notable cases in the Big 12 Conference, also have jumped at the chance to claim ignorant status. Missouri University basketball coach Quin Snyder gave the stock response to charges of NCAA infractions in his program. “Mistakes have been made in the operations of our basketball program,” he said, “and I take full responsibility for the commission of those mistakes.”

However, it was two assistants who paid the price for the mistakes by losing their jobs. Such firings are a proven, tangible way to place blame and deflect responsibility.

At Colorado University, football coach Gary Barnett is back on the job after weathering a recruiting scandal involving accusations by several women that they were sexually assaulted by football players or recruits in incidents dating back to 1997. Among Barnett’s responses was to make disparaging remarks about one of the women who alleged she was assaulted. The CU Board of Regents concluded that Barnett could be reinstated because university officials did not “knowingly sanction” the use of sex and alcohol in the recruitment of athletes.

Ah, ignorance is bliss.

To many observers, it’s difficult to believe that the officeholders, coaches or executives who find themselves under fire actually are as clueless as they claim. Former President Nixon’s effort to establish “plausible deniability” in the Watergate scandal comes to mind. Did they really not know or is their ignorance of the situation just a way to save their own necks?

If they really didn’t know, is that an excuse? It’s the responsibility of people in leadership positions to monitor the activities of those who work for them. A boss’s claim of being willing to “take responsibility” for misconduct falls a little flat, especially when the boss remains on the job while others are looking for work.

By any measure, “I didn’t know” is a weak reason to let someone off the hook. It’s too bad it has become such a common refrain.