Ernest,

If you are really concerned about preserving the data as a professional
forensics expert, then you'd make your drives (or controllers) physically
unable to write. I have never done this, but it seems like I have read
postings or webpages on cutting certain wires for disabling any possible
write capability.

Also, I don't know if that will make it impossible to mount.

Anyways, in my opinion, the correct solution is to make a mirror image of
disk and do work with it. Mounting some critical disk and using it for
possibly very timely research seems like a bad idea.

   Jeremy C. Reed
   http://bsd.reedmedia.net/