Suppose that a client comes to you with a problem: he has a computer hard drive full of child pornography, and he wants to know what to do with it. What do you tell him?
It's illegal for him to continue possessing the images. So you can't advise him to do nothing (and keep breaking the law).
The smart thing for him to do would be to destroy the hard drive (if I could, I would recommend swisscheesing it with a drill press).
But tampering with evidence is illegal under both Texas and federal law. Is it a crime to destroy the hard drive? To advise the client to do so?
Under state law (Texas Penal Code section 37.09),
A person commits an offense if, knowing that an investigation or official proceeding is pending or in progress, he: (1) alters, destroys, or conceals any record, document, or thing with intent to impair its verity, legibility, or availability as evidence in the investigation or official proceeding; …
So if you don't know that an investigation is pending or in progress, you aren't breaking Texas law by advising your client to destroy the hard drive. If you do, you are.
Under federal law, though (18 U.S.C. § 1512(c)), you don't have to know that an investigation is pending to be liable for tampering with evidence:
(c) Whoever corruptly— (1) alters, destroys, mutilates, or conceals a record, document, or other object, or attempts to do so, with the intent to impair the object’s integrity or availability for use in an official proceeding … shall be fined under this title or imprisoned not more than 20 years, or both.
What does "corruptly" mean in this context? Hell if I know. I'll bet Philip Russell didn't think he was acting corruptly when he destroyed the child-pornography-containing hard drive, and he didn't know that an investigation was ongoing. But he got charged with violating section 1512(c) and 1519—
Whoever knowingly alters, destroys, mutilates, conceals, covers up, falsifies, or makes a false entry in any record, document, or tangible object with the intent to impede, obstruct, or influence the investigation or proper administration of any matter within the jurisdiction of any department or agency of the United States or any case filed under title 11, or in relation to or contemplation of any such matter or case, shall be fined under this title, imprisoned not more than 20 years, or both.
—pled them down, and wound up suspended from practicing law and confined to his home for six months for misprision of a felony. (Things could have been much, much worse. Much.)
Your client could get the hard drive out of his own possession without destroying it by delivering it to someone who doesn't know what it contains (not you, for God's sake), but he's still arguably concealing it.
It's a crime to conceal or destroy the hard drive with the intent to make it unavailable in an investigation. So it's a crime to advise someone to destroy the hard drive with the same intent. How would the government prove your intent in advising the client? Well, you're a criminal-defense lawyer; the government would probably assume that your advice to your client was aimed at making the hard drive unavailable in an investigation. Sure, it's an invalid assumption, but that won't prevent an indictment.
You can't tell your client to do the smart thing and destroy the hard drive. (Why is it smart? Because the penalty for possessing child pornography is much more severe than the penalty for tampering with evidence, and if the client destroys the hard drive properly and keeps his mouth shut there will be no evidence that he has tampered with evidence.) You can't tell your client to do the dumb thing and keep the hard drive. What do you do?
We are problem solvers. We hate for the answer to be, "I can't answer that." But "I can't answer that" is the only possible advice in this situation.
You could, of course, instruct your client on certain aspects of the law: possession of child pornography is a crime; tampering with evidence is a crime; without the hard drive the government is likely to have a hard time proving that you tampered with evidence or that you possessed child pornography; if the government gets its hands on the hard drive they won't have a hard time proving that you possessed child pornography, which will certainly land you in prison; don't talk to anyone about the contents of the hard drive.
You can see how an appropriate instruction on the law might allow an intelligent client to draw his own conclusion.