the statements of witnesses, who alleged that they had seen marks of strangling, and produced witnesses to prove that any marks upon the body had been the result of contact with stakes in the bed of the river. Then he brought forward his own expert medical evidence, which was given by ten of the leading doctors of the day, including Sir Hans Sloane and the celebrated surgeon William Cowper. These held a different view from that of the doctors called for the prosecution, and gave their reasons for concluding that the appearance of the body was quite consistent with death by drowning.

Some described experiments they had made upon animals, which proved that when killed and thrown into the water the body sank at first and then rose to the surface, and also that drowning could take place without much water being swallowed.

As proof of the dead woman having been of a melancholy disposition and not of sound mind, letters of hers were read to the jury, but these her mother and brother would not admit were in her handwriting, since, they asserted, it did not suit her character. (See p. 85.)

The judge, Sir Henry Hatsell, in summing up confessed that he was very much puzzled, and that he perceived that “doctors do differ in their notions about these things.”

The conclusion of his remarks is worthy of quotation: “I am sensible I have omitted many things; but I am a little faint, and cannot remember any more of the evidence.”

It is not surprising that, soon after Queen Anne came to the throne, he was removed from the bench.

The jury believed the medical witnesses for the defence, and after a short discussion found Spencer Cowper and the other prisoners “Not guilty.”

To come to more modern times, the advantage of a conflict of scientific opinion to the accused was seen in the celebrated Maybrick poisoning case. At the trial evidence was given by Professor Tidy to the effect that the symptoms and appearances were not those of arsenical poisoning and that the amounts of arsenic found in the body were not greater than those present in cases where arsenical medicines had been taken months before death, and where there was no suspicion of poisoning. Although the prisoner was convicted and sentenced to death, there can be little doubt but that this evidence had an important influence in determining the subsequent alteration of the sentence to penal servitude.

There is no necessity for such scientific assistance given to the defence to degenerate into partisanship, such as was shown at the trial of Palmer for poisoning in 1856. That case was characterised by many remarkable features, the suspected person, for instance, being allowed access to the bottle in which had been placed the material taken from the body for analysis, and also being given the opportunity of attempting to destroy it.

Prior to the trial, Taylor, the chemist who was to give evidence as to the presence of poison in the body, communicated with the papers, while Herapath, one of the witnesses called for the defence, publicly accused Taylor of incompetence.

So acrid were the statements of the scientific witnesses for the defence at the trial that the judge commented in vigorous terms upon their evidence as having been given with the object of obtaining an acquittal at all costs. “It is indispensable,” he said, “to the administration of justice that a witness should not be turned into an advocate, nor an advocate into a witness.”

In another poisoning trial which took place three years later, the chemical evidence brought forward by the defence resulted in the prisoner being set free, after having been sentenced to death. In this case a doctor named Smethurst was accused of poisoning a young woman named Isabella Banks.

Dr. Taylor, who was the chief chemical witness called for the prosecution, had found arsenic in material from the body, although he could not detect any remaining in the tissues. On the other hand, Dr. B. W. Richardson, who was called as a witness for the defence, stated that arsenic was a cumulative poison, and that if it had been given for a long period, as alleged, traces must inevitably have been present. Hence in his opinion the absence of arsenic in the tissues was conclusive proof that death was not the result of slow arsenical poisoning.

The medical evidence called by the defence, also left room for some doubt as to whether death might not have been the result of dysentery, the symptoms and appearance, it was alleged, being as consistent with that cause as with arsenical poisoning.

The scientific witnesses for the defence did not succeed in convincing the jury, but after sentence of death had been passed the judge forwarded the papers to the Home Secretary, and advised that the opinion of an independent scientific authority should be taken. Accordingly the whole of the chemical and medical evidence was studied by Sir B. Brodie, whose report was that there were six reasons which led to the conclusion that Smethurst was guilty, and eight reasons which pointed in the opposite direction; and that, therefore, the impression left upon his mind, was that the proof of Smethurst’s guilt was not absolutely convincing.

The Home Secretary, on receiving this statement of opinion from his scientific referee, immediately granted a free pardon. In this case, but for the conflict of scientific opinion upon the medical and chemical evidence the prisoner would have been hanged.

Instances such as these might be largely multiplied, but the above are sufficient to show that a scientific defence may succeed in breaking down the scientific evidence brought by the prosecution in criminal cases; or, failing that, may (as in the Maybrick case) help to bring about a commutation of the sentence.

There is thus abundant justification for the plea that the poor prisoner should have the same advantages as regards scientific assistance as he now possesses in legal matters, and thus be placed on an equality with a wealthy prisoner.

It ought not to be a difficult matter to draw up a list of men of recognised standing in chemistry and medicine, who would be willing to serve in this capacity when selected by the judge in a trial.

CHAPTER II

DETECTION AND CAPTURE OF THE CRIMINAL