We finally have that detailed technical testimony, direct from the IRS technicians involved. It comes in the form of sworn affidavits, submitted in the
Judicial Watch lawsuit:
http://www.judicialwatch.org/wp-content/uploads/2014/08/Judicial-Watch-v.-IRS-01559.pdf
The second statement is the most interesting one, from the forensics technician (John Minsek, page 8 of the .pdf). I was surprised at how far he went to try to recover Lerner's drive. Not only did he use that "specialized hardware" I mentioned, he actually did use a "clean room" of sorts (clean box?), and tried replacing both the controller card and the heads, carefully ensuring he had an identical model and firmware revision according to his testimony.
His efforts were unsuccessful. He was experiencing some sort of controller error that kept it from ever entering a ready state. I don't know if that indicates a more serious hardware problem, or is merely that "luck of the draw" issue I mention when trying to swap controller cards. Either way, he was ultimately unable to recover any data at all from the drive. It does show that the problem was beyond merely writing bad data to the drive, or reformatting it.
Finally, at one point I speculated that when the IRS tech said the drive was "scratched", he might have meant he wiped the drive and not that it was physically damaged. I was wrong about that. (This is related to me not expecting the IRS to try a clean room recovery.) Today's affidavits report that a drive platter was physically scored. They also confirm that there was no evidence of intentional physical damage.
Anyway, aside from the implications for this story, I found the second statement interesting in its own right. It is quite detailed. It's worth a read if you'd like insight into advanced drive recovery tactics.