Who is responsible in the event of an accident?

Correct answer: The driver of the vehicle.

The driver is responsible. Anyone driving a motor vehicle is responsible for the damage they cause while driving. That responsibility does not shift to the owner or insurance policyholder, although the owner may also be liable in specific cases, such as when the vehicle is uninsured.

Real Decreto Legislativo 8/2004, de 29 de octubre, por el que se aprueba el texto refundido de la Ley sobre responsabilidad civil y seguro en la circulación de vehículos a motor