In an effort to get a shareholder class-action lawsuit related to options backdating at United Health (NYSE: UNH) dismissed, former CEO William McGuire is claiming that, gee, golly, he just didn't know much about them fancydangled options. He's just a doctor!

The Star Tribune reports that his lawyers have filed a brief stating, in part, that "Dr. McGuire has no formal training or degrees in finance, accounting or law. His only professional training is as a medical doctor with a specialty in pulmonology."

Interesting. I wonder whether Mr. McGuire argued that he should be given a smaller compensation than other CEOs because he had no training in anything related to business. I somehow doubt it. The "I have no idea what happened! I don't know anything! I'm an idiot!" defense has become quite common in white-collar crime cases. After making a variation on mark-to-market accounting a prerequisite for joining Enron, former CEO Jeff Skilling later claimed that he "wasn't an accountant" in defending the fraudulent practices of the company.

At some point, the top men in charge have to be responsible for fraudulent conduct at their companies. If he didn't understand the accounting, he should have made it his business to understand it. He was the CEO.

As its CEO, William McGuire transformed UnitedHealth Group Inc. (NYSE: UNH) into a healthcare powerhouse. In the process, of course, he became a billionaire – i.e., through stock option compensation.

Well, now he is out of the corporate suite. As has been the case with many CEOs, McGuire has been ensnared in the options backdating scandal. In the past week, other high-profile CEOs have departed because of the scandal, such as the CEOs of McAfee Inc. (NYSE: MFE) and CNet Networks Inc. (NASDAQ: CNET).

Given the huge numbers, there was nowhere for McGuire to hide.

UnitedHealth hired an outside law firm to conduct an investigation. Although the language was qualified -- using terms such as "likely" -- no doubt the findings were not helpful for McGuire and the damage was done. Besides, in the highly regulated industry of healthcare, it is important to go beyond just being law-abiding.

Interestingly enough, if there was no backdating, McGuire would probably still be a billionaire. He certainly was a standout CEO. But, in the world of mega compensation, there is always the temptation to push the envelope, which, in the post-Enron world, is a huge risk.

Tom Taulli is the author of various books, including the Complete M&A Handbook and operates InvestorOffering.com.