It is not always understood that the term physical evidence embraces any and all objects, living or inanimate. A knife, gun, signature, or burglar tool is immediately recognized as physical evidence. Less often is it considered that dust, microscopic fragments of all types, even an odor, may equally be physical evidence and often the most important of all. It is well established that the most useful types of physical evidence are generally microscopic in dimensions, that is, not noticeable by the eye and, therefore, most likely to be overlooked by the criminal and by the investigator. For this reason, microscopic evidence persists for months or years after all other evidence has been removed and found inconclusive. Naturally, there are limitations to the time of collecting microscopic evidence as it may be lost or decayed. The exercise of judgment as to the possibility or profit of delayed action in collecting the evidence is a field in which the expert investigator should judge.
As used in the passage, the phrase well established most nearly means
