Where I work...
As part of discovery, the legal notice to hold info is sent the corp.
The corp sends a blanket email directing everyone to stop deleting anything (emails, reports, any electronic communication, or paper copy, etc) related to a certain topic until the hold is lifted.
This process is covered in a pretty standard training exercise here. Our corp makes it mandatory to retake the online lecture every couple years.
Who knows if this guy really did anything wrong. That's what his day in court is for.
I tend to suspect what Bryan says. They are hoping to squeeze out some accusation or secret they couldn't discover through normal channels. Probably just due to ignorance. They are after all lawyers, not engineers. Same problem at the EPA, which writes self contradictory rules and physically impossible test procedures. Then we have to beg them to fix it.