In Analysis and Testing In Accident Reconstruction, accident reconstruction expert witnesses at Technology Associates explain the nature of engineering analysis:
Straightforward as the above reasoning is (see 7/16/09 blog entry), it nevertheless constitutes a valid (though simple) example of engineering analysis. Now let us consider what it would take to demonstrate the defect of the steps by testing rather than by analysis. To do this, there must first be devised a suitable test procedure, and this can be arrived at only by further analysis-which is another word for organized and systematic thinking with relevant technical considerations taken into account. From this analysis, there emerged the following requirements:
1. The tests must be done with different subjects, who must not know they are being tested and must not observe each other performing the descent of the stairs-else their performance will be affected, and so will not represent “normal” descent of the stairs by an unwarned person.
2. The descent is dangerous because of the shallowness of the treads, and there seems to be no practical way of eliminating the danger without creating special conditions-such as the use of safety nets-which will alert the subjects to the fact that something unusual is going on, and so prejudice the tests.
3. If stumbling actually occurs during the test, the effects will be quite variable. In many cases, the stumbler will regain his balance before injury occurs. To be indicative, the tests must be repeated with enough subjects so that injury, or near-injury, occurs in some cases-and this is of course unacceptable.