Arizona state motorcycle helmet laws, ARS 28-964, state it is not required for a person aged 18 years or older to wear a helmet while riding a motorcycle but for 17 yrs. old and younger must wear helmets. All motorcyclists and passengers, regardless of their age, must wear a transparent face shield, goggles, and glasses while riding.It is not illegal for an adult to drive a motorcycle without a helmet, but most often it is found to be negligent if an AZ motorcycle accident involves a head injury while riding without a helmet.
Fault is negligence that was a cause of the motorcyclist’s injury. Negligence is the failure to use reasonable care (the failure to act as a reasonably careful person would act under the circumstances). The most common situation is when the car driver negligently causes injury to the motorcyclist and thus is at fault. The defense if no helmet is being worn and a head injury occurs is that a helmet would have avoided the head injury, so the motorcyclist is ALSO at fault.
In AZ, each of the parties must prove the fault of the other, then the judge or jury will weigh (apportion) the evidence and make a percentage determination as to which one is at fault and to what degree for the injury or injuries. E.g., the car driver may be 100% at fault for the cyclist’s broken leg and the car and motorcycle drivers are each 50% at fault for the head injury. See Fault 11, Determining Relative Degrees of Fault (Comparative Fault), RAJI(Civil) 6th.