2.5. Download 1TB of cute cat videos onto HDD.
Example, you could fill the drive with movies or music
And/or basically any other "random" files you can get your hands on. /endofthread. Seriously
And if you're really that paranoid, do it several times over. (PS: Just in case this isn't obvious, it would of course be wise
not to write illegally downloaded "random data" to the drive.

)
I know a lot of people (like to?) think "the government" are a bunch of incompetent nincompoops but they really aren't (some percentage of the "policymakers" might be, but not the people who do the "actual work"). Anything that isn't actually "random" data (and I do mean "data", of the sort someone might actually store on their hard drive in the real world,
not just "random
bits") is going to look very obvious to anyone working for "the government" who's given the the drive for analysis. I mean, you don't think they're going to give it to the arresting LEO or a rookie FBI agent who majored in poli sci in college and has been on the job for 2 weeks, do you?
And if you clone a new drive to the old one, don't forget you'll have to reset the S.M.A.R.T. data to match... I myself don't know how to do that (never having had a reason to do so), but I believe that is do-able, though not particularly straightforward... Otherwise, it'll look just a wee bit strange that your hard drive's "data" is saying "I'm only two weeks old", but the SMART table says "I've been used heavily for two years..."
And last, but by no means least, don't get hung up on what is and isn't "proof". "Proof" is simply admissible evidence sufficient to convince a judge or a jury, not to counter every, er,
imaginative "possible explanation" a bunch of random adolescent-geeks-on-the-Internet come up with, with or without benefit of recreational psychoative substances...