CRIME DETECTION

Otago Daily Times, Issue 21976, 10 June 1933, Page 20

CRIME DETECTION

APPLICATION OF SCIENCE IDENTIFYING BLOODSTAINS. Facts concerning the part played by medical science in the detection of criminals were given by Dr P. P. Lynch, pathologist at Wellington Hospital, in an address delivered to the Wellington Law Students’ Society. He dealt particularly with the identification of bloodstains, and the latest advances for determining their origin. . ' Forensic medicine had in recent years advanced in step with medical science as a whole, Dr Lynch said. But one of the most important advances had been the identification of bloodstains. In many trials involving charges of murder and manslaughter, it was of the very greatest importance that bloodstains on clothing or weapons found in the possession of suspected persons should be identified as being ol human origin or otherwise. Not earlier than 1900 was identification of the origin of blood possible. THE PRECIPITIN TEST.

This identification was made possible by means of two tests, one by observing chemical reactions common to blood from any mammalian source, and the other was a"biological or precipitin test. Explaining the precipitin test, Dr Lynch said that the procedure was to inject a human protein into an animal, say, a rabbit, and then after a lapse of time to separate the scrum from, the blood of the animaj. If this serum were added to the original protein' injected, the two fluids would not mix clearly and evenly, but a definite precipitation and cloudiness would take place. No precipitation of oven the minutest kind took place when other than human protein were added. .' •

Using these two, tests, the origin of bloodstains could be determined with certainty. The tests in European countries were carried out in many instances by medical-legal institutes. Dr Lynch dealt at some length with tests of biological groupings of blood, which promised to be of some import ance. From certain phenomena, it had been noted that the blood of the human species could be divided into four groups, according to how the red cells were grouped. For instance, it was found that group IV predominated in European peoples, group II in a race such ns the Australian aboriginal, and group 111 in Asiatic races. BLOOD ON A RAZOR.

The advantage of this test was that it was not only able to determine whether bloodstains belonged to the human species or not, but it was also possible to determine broadly to what human race the blood belonged. A few years ago in England a man, charged with murder, was found with a blood-stained razor in his possession. He attributed the state of the razor tp careless shaving, but the Crown said got there in a less innocent way, and a conviction was secured when it was shown that the blood of the victim and the stains on jbhe razor belonged to the same blood group. Another advance made was the identification of hair, Dr Lynch continued. Usually it was possible to say whether it was 'human hair or from a horse or a dog. This was determined by a microscopic examination. A study of the structure of the human hair, and making comparative studies of hair of animals, enabled the identification to be made, BULLETS IDENTIFIED, Identification of projectiles was now entering into the scope of forensic medicine. It was strange that this was not left to those who manufactured and dealt in guns, but two cases in recent years, one a New Zealand one, had been determined by medical men. The New Zealand case was irt Auckland some 15 or 10 years ago, when a postmaster was found shot dead. The bullet was extracted from his body, and the markings on it were carefully examined and coinpared with those on a bullet fired from a weapon found in the possession of a suspected man. This evidence, combined with that of certain fingerprints, led to a conviction being secured by the Crown. The other case, and a more important one, was that following the murder of the Sirdar of Egypt, Sir Le e Stock, in 1026, by disaffected students. Many months passed before the murderers were arrested, and their conviction was secured in exactly the same way as in what had now come to be known as the Auckland case. \ i —■.