Science and the Criminal

by C. Ainsworth Mitchell

For instance, suppose a stain on the clothes of a person accused of murder were examined by a chemist for the prosecution and found to consist of blood. The fact would tell against the accused, even though the witness (as in a recent case) could express no opinion whether it was human blood, or the blood of an animal. Assuming in this hypothetical trial that the blood stain was really due to rabbit’s blood, another chemist representing the prisoner might be acquainted with the comparatively recent physiological methods of distinguishing between the blood of different animals, and thus be able to prove the real nature of the blood stain and break one of the links in the chain of evidence.

In most of the important criminal trials the scientific evidence is given by more than one witness, and the possibility of mistake is thus greatly reduced, but this is not invariably the rule.

Scientific criticism derived from a first-hand examination of the material would be of much more value than the criticism of the statement of the results, and might have considerable weight upon the conclusions of the jury.

A defending counsel cross-examining a scientific witness is usually dealing with an unfamiliar subject, and lacks the specialised knowledge that would enable him to point out the weak points in the evidence.

When a wealthy person is on trial, however, the counsel has the advantage of getting the best expert advice upon the scientific matters put forward in evidence, and is thus able to lay stress on all that will help his client, but a poor prisoner lacks this advantage, and therefore runs a greater chance of being convicted.

An early trial in which the prisoner owed his acquittal to a conflict of scientific evidence was that of Spencer Cowper, the grandfather of Cowper, the poet, who was tried at the Hertford Assizes in 1699 for the murder of a young gentlewoman named Sarah Stout.

With Cowper were also tried several of his friends, whose remarks having been overheard had suggested that they were aware of what had happened to the girl.

Cowper, who was a barrister, defended himself and incidentally his companions. The story told by the prosecution was that at the previous Assizes the prisoner had stayed for a night at the house of Mrs. Stout, the mother of Sarah Stout. The servant-maid stated that she had been told to prepare Mr. Cowper’s bed, and that when she came downstairs again, it then being about eleven o’clock in the evening, he had gone out, presumably with Sarah Stout, who was never again seen alive. The next day her dead body was found floating upon the river.

The condition of the body was, it was asserted, conclusive proof that she had been strangled and then thrown into the water; for, to quote the words of the counsel for the prosecution, “when her body came to be viewed it was very much wondered at; for in the first place it is contrary to nature that any persons that drown themselves should float upon the water. We have sufficient evidence that it is a thing that never was; if persons come alive into the water, then they sink; if dead, then they swim. At first it was thought that such an accident might happen though they could not imagine any cause for this woman to do so, who had so great prosperity, had so good an estate, and had no occasion to do an action upon herself so wicked and so barbarous. Upon view of the body, it did appear there had been violence used to the woman; there was a crease round her neck, she was bruised about her ear; so that it did seem as if she had been strangled either by hands or a rope.”

The evidence brought forward to support the theory that Sarah Stout had been killed, before being thrown into the water, included that of several local doctors who had examined the body, and also that of several London doctors who were called in as expert witnesses.