The BIOS (including the boot-selection page) is password protected. Even when a CD-ROM is physically attached, booting from CD-ROM/USB requires the system password. Oh, and the hard disk incorporates password protection, which is configured.

Easy enough for qualified personnel to defeat (along with the BIOS-level HDD password protection? Probably). That is, the nerd back at the police lab - not the PD's street soldiers.

Go ahead - give 'em a hacker tool on a stick. Let 'em feel like they're technically competent to conduct field investigations into an area which I'll wager most of them don't even remotely understand. Oh, and let me raise questions at trial into the safeguards in place to prevent officers from inadvertantly/intentionally corrupting the contents of the filesystems they intend to investigate in the field.

(I'm assuming their hacker's tool can automagically recognize and search ext3, ext4, jfs, ufs, xfs, reiserfs, FAT16, FAT32, NTFS, etc. . . . and let us not forget software-based filesystem encryption for many of the aforementioned filesystems).

Well I guess the prior information that there was something that looked like a face under the blurred blob could be used for some kind of statisitcal estimation of how the face might have looked. I think that much less information is needed to extract biometric features from a blurred picture, than to do real un-blurring. Has something like that been used in practice?
It could work somehow like the 'de-pixelization' of license plates where AFAIK the most likely licenseplate number is estimated instead of doing real (impossible) de-pixelization.