THE MICROSCOPE AS A CRIMINAL DETECTIVE.

Thames Star, Volume VII, Issue 1947, 1 April 1875, Page 4

THE MICROSCOPE AS A CRIMINAL DETECTIVE.

The anuals of criminal jurisprudence furnish an abundance of cases iv which the microscope, in the hands of an expert, has been the means of eliciting missing | links in the circumstantial evidence point- j ing to the guilt of the accused. Instances are cited where the instrument has shown hairs, clinging to the edge of an axe, to be those of a human being, in direct contradiction of the statement of the prisoner, who has ascribed them to some animal; and similar scrutiny of fresh blood upon clothing has proved the origin of the stain beyond a reasonable doubt When blood, however, has once become dry, soveral authorities assert.that ibis impossible to distinguish it from tbat of the ox, pig, sheep, horse or goat. It is urged that the ..differences- between the average sizes of their corpuscles are too irregular to measure accurately, and that a man's life should not be put in question on the uncertain calculation of a blood corpuscle's ratio of contraction iv drying. In opposition to ihese views are some recent experiments made by I)r Joseph G-. liichardsqn, of Philadelphia. This investigation disposes of the first objection above mentioned by pointing out that, while it may be valid as regards i'eeblyniagniHed blood discs, it becomes void when these bodies are amplified 3,000 times. ' [Regarding the second, he stamps it as incorreetyand cites a ease in which seven human blood discs, whose mean diameter had been accurately determined at 1-3236 of an inch, were subsequently computed to average 1-3260, or only 1-352292 of an inch less than their actual magnitude. Dr. Eichardson also points out, with reference to the last objection, tbat all the blood discs likely to bo mistaken for those of man, 1 eing normally smaller, instead of contracting they would have to expand to become conformed to those of human blood. This expansion does not occur, so that the only possible mistake in diagnosis would be to suppose that ox blood were present when man's blood had actually been shed ; so that at the wbrst we might contribute to a criminal's escape, but never to the punish- { ment of an innocent person. In order to afford a positive demonstration of the facts, Dr Richardson obtained from each of two friends, three specimens of blood clots, from tho veins of a man, an ox, and a sheep respectively, selected without his knowledge. By microscopical examination he was able to determine, with perfect accuracy, the i origin of "each sample. The corpuscles of j human blood aiveraged -,1.3430, with a maximum of 1.3174, and a minimum of 1.3636 of an inch; those of the ox's blood gave a mean measurement of 1.4662, with a maximum of 1.4347 and a minimum of 1.4874; while those of the sheep's blood afforded a mean of 1.5952, with a maximum of 1.5405 and a minimum of 1.6451 of an inch. From these and other experiments, Er. Bichardson concludes that, since the red blood globules of the pig, ox, red deer, cat, horse, sheep, and goat " are all so much smaller than even the ordinary minimum size of the human red disc, as computed in my investigations, we are now able, by the , aid of high ;powers of the microscope and Tinder favourable circumstances, positively to distinguish stains produced by human blood from those caused by the blood of any one of the animals juit enumerated; and this even after a lapse of five years (at least) from the date of their primary production."—Scientific American.