DBAN takes way too long, like 5 - 10 hours on your average 300 - 500 GB hard drive, to be an effective defense during a raid. Your best option at that point is degaussing with a strong magnet. If you have incriminating evidence on your hard drive now, you should DBAN it now and set up full disk encryption. Don't wait until you are getting raided. Sure, there are attacks on encrypted drives too, as we're discussing in AnonymousAddict's thread, but it makes LE's job a few orders of magnitude harder than the solution you're currently using, and unless you're a terrorist or cartel king pin, they're probably not waiting outside your door, prepared for a cold boot attack.