Recent microtechniques in forensic science.

Forensie science is synthetic, depending on all the other sciences for development of its basic techniques, and it is original chiefly in that it adapts the techniques of other sciences to its unique and specialized uses. One of its major branches, criminalistics, does have a special aim which is not the same as that of other applied sciences, namely the individualization of a sample of evidence, which is equivalent to the determination of the source of the item of evidence. Individualization goes beyond identification; in fact it starts where identification leaves off, and this is the feature of criminalistics whieh makes it unique and requires for it a philosophy and a modus operandi that are not direetly available from the developments of the other seiences. In effect, it is an application of comparison between samples of known and unknown origin, taking into account the fine details, morphoIogical or chemical, that may be found in eommon between two samples of identical origin and not common to items from different sources. When only dass distinctions are being sought, as in chemical identification, this kind of minutia would be disregarded. In general, such comparisons are merely extensions under controlled conditions of the same basic procedures that are of utility in chemistry, geology, or biology. This makes it very diffieult to make any claims for originality for the teehniques used by the criminalist. His applications tend tobe original, and his interpretations may also be, but only oceasionally will he invade the realm of development of new or radieal basie rnethods. Criminalisties is often equated with chemistry, and it is sometimes assumed that the ehernist is automatieally a erirninalist. Apart from the fact that this is simply not true, it is necessary to realize that it is the microchemist more than the ehernist who is most closely related to the criminalist. Virtually all evidence samples are small, often vanishingly so, and the ehernist who has no speeific knowledge of microteehniques is almost as helpless as if he did not know any ehemistry. However, there is an important differenee between the research approach of the mierochemist and tha t of the criminalist. Most microchernists are eoneerned with specific and sophisticated techniques for identifying and determining specific chemical entities, often in systems of very restricted origin. They are rarely interested in identifying or determining some item in relation to the entire universe of similar items. This is the job of the eriminalist. His unknowns tend to be general unknowns without much indication of the restricted dass to which they belong. He is not interested in the molybdenum content of the steel; rather, he must determine the following faetors about the minute evidence fragment: (i) if it is metal,