Probably a prosecutor that works for some local government that could be also be liable for letting Uber operate that car in their jurisdiction. I imagine that discussion happened.
The UK actually has a law against this, see "Causing Death by Careless or Inconsiderate Driving (Section 2B of the Road Traffic Act 1988, amended by the Road Safety Act 2006, s. 20)" here: http://www.brake.org.uk/news/15-facts-a-resources/facts/497-...
It means you can be prosecuted for causing a death in a moment of inattention. It's a bad law from both sides: As you can see from the link above it doesn't satisfy the charity (who want stronger penalties), while at the same time being a catch-all law which could catch anyone out who drives, even if they are generally very cautious drivers.
By the way I should add there was already a separate law for causing death by dangerous driving.
One more reason why we need self-driving cars I suppose.
