Why is everyone concentrating on the software? There was a human in charge and the car was exceeding the speed limit. That sounds like either driving without due care and attention or reckless driving. After all the driver's reaction time is almost certain to be much longer when supervising an autonomous car than when driving directly making it much more important to adhere to the rules.

And if it can be shown that it was company policy to allow the cars to exceed the speed limit then heads should roll all the way to the top of the company.