In Kansas, the law does not require motorcyclists to wear a helmet. Therefore, no comparative fault can be assessed against the rider if the accident happened in Kansas. Still, it is wise to wear a helmet. Even though a Kansas jury cannot assess fault for failing to wear a helmet, it is not uncommon for members of the jury to carry some prejudice against a rider who chose not to wear a helmet. This may cause the jury to have a lesser opinion of your claimed injuries and the resulting damages.
Missouri law does require motorcyclists to wear a helmet. Therefore, if the motorcycle accident occurs in Missouri and the rider suffers injuries related to head trauma, the defendant can argue that the plaintiff was partially at fault for causing his or her own injuries and damages by not wearing a helmet. A helmet-less rider that suffers traumatic brain injury, concussion, or other injury to his head as a result of the negligence or inattention of another driver may still be able to recover damages from that driver, including payment for medical expenses, but his/her total recovery could be reduced (sometimes significantly) by the percentage of fault assessed to the motorcyclist as a result of failing to wear their helmet. This is called “comparative fault.” On the other hand, if the injuries were unrelated to the head, such as a fractured leg or a herniated spinal disc, then it is unlikely that any comparative fault would be assessed for failure to wear a helmet.