Ok, real talk about the "CP on a used HDD; a program just happened to start sharing it for me."
Do I believe he could have bought weird shit on a HDD and been surprised about it? Yes. Absolutely. I wouldn't even be shocked if it happened.
Do I believe he didn't format his shiny new HDD? No way.
If he did do a format, and the FBI scanned the empty space and found shit? I could see this happening and he'd still be fucked. (But they'd have to have a good reason to raid him in the first place, so... unlikely.)
Is it odd that he refused to speak to the police? Fuck no, it's the smartest thing he could do. The FBI / Police are not your friends, they can and will lie to you, and they have a vested moral and economic interest in getting you arrested and arraigned, even if they know you're innocent.
Do I think he had a program that just started sharing the contents of his HDD?
... Maybe.
It depends on the program.
If it's Limewire or whatnot, and he happened to be running the same program and it was pointed at the same old folder for downloads? It could start sharing without him knowing.
If it's Bittorrent, and he's got it set up to auto-load torrents in a given folder? That just happened to have old torrents? Ok.
If it's Dropbox, Google Drive, or something similar, and it decided to re-use an existing, CP filled, folder? I could see that?
If it was me, I'd be asking my lawyer to get a forensics expert to look at the GUID of the owner of any files (torrent, downloaded, etc) on the filesystem, their creation dates, NTFS permissions, etc. If they came from a previous OS installation they'll have really weird owners / people with really permissions like SEC 5-5134-15134-415-1-481-41 instead of Computer/BOB. Log files for when files were uploaded to Dropbox / Google Drive would also be useful; if it was all due to a new HDD, they would all be uploaded in one huge burst.
Without violating powerlevels, back about 10, 15 years ago there used to be a Japanese P2P network called WinNY or Share, depending on which revision it was. It wasn't dissimilar to Limewire et all, you would cache parts of the "network" and share files between each other, also had a built in dynamically distributed 2ch/4chan/8ch thing. The motto was "they can't arrest ALL of us."
The way it'd work for file sharing is you'd set up a keyword search, usually of the format of some game or album or what have you. "Naruto Episode 5," or "NewPornGame by Manufacturername."
But you could do something exceptional, like put in a keyword like "big ol' titties" or "brown skinned elf chicks" or "That One Manga Artist You're Obsessed with Collecting." And then any files flagged as such would download. Of course, there was nothing stopping people from putting... anything in those zip files. I never saw anything illegal, but occasionally people's dox, or shock videos, or what have you would be shoved in and mislabeled.
(Rarest find? The video tubgirl came from. It was supposed to be a Ranma 1/2 episode.)
Now... in another timeline, where a powerdrill hadn't been taken to a few DVD-R spindles a few years back just in case? Say I got raided, and DVDs and HDDs got taken. "No officer, I didn't download that, I put in a keyword and it auto downloaded every file with that name on the network..."
Yeah. Internet was a very dumb place 10 years ago. The VA's brother is probably lying and still fucked, but it's not ENTIRELY outside the realm of possibility.
