Putting the developers on the line would mean that they'd never want to sign the software off, just in case anything ever did go wrong.
I would have a hard time doing this, either via law or even as a juror at a trial. We all know that developers do as they're told. Sign off means that they followed the company spec per managlement. Now if manglement (up to to and actually including board) were culpable then that's a good thing.