In a sense the lawyer is right. Negligence cannot, by definition be intentional conduct, so it would be impossible to conspire to be negligent.
For instance, you and your buddy are driving down the road, and decide to drive real fast and erratically. Your careless driving results in a collision with another care. Did you agree (agreement is the touchstone for conspiracy) to wreck the car? No you only agreed to drive erratically, which is intentional conduct; you did not agree to the collision, an unitentional action. I note however, in a consiracy one is generally liable for the foreseeable acts of co-conspirators--so even if you did not agree to crash the car, both would still be liable, becuase a collision is a reaonable foreseeable act.
Change the hypo a little, and you agree to collide with another car--this is intentional conduct, and you have conspired to do such--but since the act was intentional it cannot therefore be negligent.
The porblem is that the dead girl's lawyer is not very savy, or the media is not fully reporting the story. Just becuase the tortfeasors could not conspire does not mean they are not liable.
I agree lawyers make things overly complicated--espetially bad lawyers.
