[nknight]

In civil cases, once you know or have reasonable cause to suspect a court case is imminent, you're technically supposed to act to preserve evidence, and not doing so can lead to sanctions, even if the evidence was destroyed as part of routine policy.

I'm less clear on how evidence tampering is dealt with in criminal law.

[dkokelley]

In a criminal case (and likely in the worst of criminal cases), the suspect has no idea when the FBI will come bursting through the door to arrest him/her and seize hard drives. A dead-man's switch would be impossible to prevent in this scenario (aside from never using one in the first place).