Cars crash when one or more of three components in the system fail: drivers, autos, or the roads they run on.

Major failures can cost millions. Lawyers call expert witnesses. Behavioral psychologists investigate drivers; engineers examine the dynamics and design of cars and highways. The science of crash investigation got serious when UCLA founded a Traffic and Safety Institute in the mid-'50s.

Doctor of engineering, William Blythe, a leader in the field, has investigated crashes for the last 19 years. "When I began," he says, "there were two or three others in California. Today there are 20 or 30. I don't know that the insurance crisis has affected the business, but increasingly sophisticated legal work is being done in the courts. Yet judges still accept the credentials of 'expert' witnesses too lightly. A lawyer must be very careful who he engages -- supposing, of course, he wishes an honest opinion in the first place," says Dr. Blythe. "For all the sophistication of crash investigation today, I liken our times to those in Europe when barbers practiced medicine."

The good doctor should know, yet he seems harsh on himself when you take into account the case of Sgt. Roderick Sinclair and the Secret Service. In this case, Dr. Blythe worked closely with crash investigator Paul Kayfetz, who, says Dr. Blythe, "is a lawyer, a certified genius, a perfectionist, and a man who any egocentric trial lawyer has difficulty working with, since his peculiar expertise will tend to take over most of a case."