Remember kids... always wear a helmet. (The almighty bikeradar helmet thread)

The doctors opinion is no more valid than yours, it is pure guess work.

A parked car is a parked car, don't see the relevance of blaming the driver or why the car was parked where it was.
Doctors' opinions are always useful but they rarely have enough information about the crash to make an accurate evaluation. If the rider hit a parked car while going at time-trial speed the outcome would depend on the crash dynamics.
If he hit the car head first he would be likely to die, helmet or no helmet.
If he went over the top and landed in the road he would be more likely to survive, helmet or no helmet.