Think quickly: What do Martha Stewart (search) and I. Lewis "Scooter" Libby (search) have in common? Well, at least based on the "charges" against Libby, not a crime — but covering up a crime.

When you obstruct justice, the idea is you are obstructing getting at the truth.

That's why the problem for Martha wasn't that she might have sold stock in a company based on inside information — that stock sale never came up — only that she might have tried to cover her tracks long after the sale was made.

It's the same thing that brought down Richard Nixon (search) — not a break-in into Democratic National Committee headquarters, but the administration's efforts subsequently to cover up all activity "since" that break-in.

For Libby, the issue is whether he lied about what he did "after" the fact. Again, it's not so much whether he did or did not reveal a CIA operative's name, but if he obstructed justice by impeding the investigation into whether he did.

I know it's confusing. But here's what is not: The crime isn't the act that gets you. It's what you did, or didn't do, after it.

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Neil Cavuto serves as senior vice president, anchor and managing editor for both FOX News Channel (FNC) and FOX Business Network (FBN). He is anchor of FNC's Your World with Cavuto - the number one rated cable news program for the 4 p.m. timeslot - as well as the FNC Saturday show Cavuto on Business. He also hosts Cavuto on FBN weeknights at 8 p.m. In addition to anchoring daily programs and breaking news specials on FNC and FBN, Cavuto oversees business news content for both networks and FNC's weekend business shows, including Bulls & Bears, Forbes on Fox, and Cashin' In. Click here for more on Neil Cavuto.