I would say that at virtually every 'serious' collision these days, the Police sieze the mobile phone from all parties involved. They are then tested to see if they were being used at the time of the incident.
Slightly different tact,
I remember one where a beautiful 24yr old died after a collision with a vehicle. She had been texting all evening on her phone including up to the collision as she crossed the road.
The context of the texts were a virtual rundown of her getting more and more drunk as the evening went on.
Good evidence, but a very sad affair.......especially where her parents were concerned!