KINEMATICS

Considering the immense cost to society of murder in general, and serial murder in particular, it is remarkable how scant is the research on causation. Apart from indicators that extraordinarily brutal childhood abuse and severe and recurrent traumatic brain injury figure with monotonous regularity in backgrounds of perpetrators, we know next to nothing about etiology.

In a similar way, billions of dollars are consumed annually in medical care and compensation for victims of motor vehicle accidents, but the medical (as distinct from engineering) research literature on kinematics is restricted to a handful of quality papers.

PRACTICE POINT

The medical kinematics literature is so rudimentary that it can be largely ignored for purposes of establishing causation of MVA personal injury

Engineers are not trained to factor in the magnification effect on relatively minor of pre-existing "thin skull" medical conditions, whether physical or psychological. Physicians must be ones eventually to integrate biophysics with neuropsychology.

However, even a couple of fundamental concepts recently addressed in the medical research literature remain in the early stages of development.

On the relationship between vehicle damage and severity of occupant injury, a current German paper⁹ suggested that the stresses involved in rear-ending collisions which regularly result in cervical whiplash are analogous to those of fairground bumper cars.

The design of the research and the structure of the arguments are reminiscent of the previously digested (Medical Litigation News, Volume 1,Issue 6) Canadian paper which proposed that the forces were comparable with those of plopping in a chair.

The latter research, which was funded by the provincial motor-vehicle insurer and used to perpetuate the myth that personal injury is proportional to vehicle damage, is now largely discredited.

PRACTICE POINT

In low velocity motor vehicle impact, the potential for occupant injury is in many circumstances INVERSELY proportional to the amount of vehicle damage

The arguments in these papers pay scant attention to crush distance, a measure of the absorption of kinetic energy by compression of the vehicle¹⁰. As in the extremes of a small car rear-ended either when bumper-to-bumper with a heavy truck or on sheet ice, the G forces on the occupants are inversely proportional to the vehicle damage.

Occupant preparedness for impact has similarly been given scant attention in MVA simulation using healthy volunteers. As noted previously (Medical Litigation News, Volume 1, Issue 6), severity of symptoms has been correlated with lack of preparedness, as is most common in rear-ending accidents.

Nearly 50 years ago, researchers demonstrated¹¹ that sudden sounds could, within a twentieth of a second, trigger a "startle pattern" of activity in the muscles of the neck. Could the empirically demonstrated lesser torque in the neck of a prepared volunteer occur because of a similar mechanism?

PRACTICE POINT

Unpreparedness for impact is a hitherto neglected factor which may explain the greater severity of symptoms after rear-ending

Although they do not know exactly when, volunteers do know they will be traumatised. No attempt has hitherto been made to quantify the effect of such vigilance on the maintenance of protective reflexes². Perhaps the simulations should be repeated with volunteers still sitting upright but asleep.