For MAY 2002 issue

SCIENCE IN CRIME DETECTION-106

HANGING DOGS TO LEARN MORE ABOUT HANGING

‑Dr. Anil Aggrawal

This time I am going to tell you about an extremely interesting experiment which has recently been done in Japan, by two scientists, Akiko Sawaguchi and Toshiko Sawaguchi. They are a mother and daughter team, and both are involved in forensic work. It is very rare that mother and daughter have both worked as forensic pathologists. In my knowledge there is only one previous example in which a parent and a child worked both as forensic pathologists. And even that example is not of a mother and a daughter; that is of a father and a son.

This father and son team was that of John Glaister I (also known as John Glaister Senior) (1856-1932) and John Glaister II (also known as John Glaister Junior) (May 1892 – 4 October 1971). They were both Regius Professors of Forensic Medicine at the University of Glasgow. John Glaister Senior was the 4th Regius Professor from 1898 till 1931. And after him, his son, John Glaister Junior became professor and remained professor till 1962. Together, the father and son team occupied the forensic medicine chair at the University of Glasgow for an incredible 65 years! And both were very competent forensic experts, both being involved in world famous cases of detection.

Coming to the work of Sawaguchis. They have done some interesting work in the field of asphyxia. But let us first understand, what asphyxia is. Putting plainly and succinctly, it is a condition which results, when the supply of air is cut off from the lungs. It can happen in a number of ways. One of the most familiar is hanging. When one hangs by the neck, he essentially cuts off the supply of air from his lungs, by means of the ligature, which he ties round his neck. This ligature is tightened by the weight of his body, thus compressing the windpipe completely. Other forms of asphyxia are drowning, gagging, choking etc. Gagging is a situation when somebody pushes a cloth down the throat of a victim, and choking is a condition when something – most commonly a food particle – slips in the windpipe, blocking it.

Irrespective of how asphyxia is produced, one thing is common that happens in all. The blood oxygen concentration comes down drastically. This is understandable as the intake of air is completely stopped. Simultaneously there is an increase in the carbon dioxide concentration of the blood. This is also clearly explained by the fact that the blood can no more deliver the waste products in to the lungs.

The readers may want to know why in the first place is the research in asphyxia needed at all? Well, consider the following situation: A newly married woman is found hanged in her bedroom. The story of her in-laws is that she has committed suicide by hanging. At the same time her parents insist that she was first killed by some other method, and then hoisted up to simulate hanging. Of course a thorough post-mortem can solve this problem very easily. But if we do some research in asphyxia, we will have one more way, in which to solve this problem. Let me illustrate with an example. We have just seen that in “true asphyxia”, the blood oxygen comes down drastically while the blood carbon dioxide increases. So can’t we estimate the blood oxygen and carbon dioxide levels to know if the lady truly hanged herself or not? Surely if she hanged herself, she would have died of asphyxia and her blood oxygen would show a decrease and blood carbon dioxide an increase. And if she died in any other manner these changes would not be there. Presto! The problem is solved.

But unfortunately things are not as simple as that. After death, the blood gases tend to diffuse in and out of blood vessels very easily and this disturbs the postmortem concentration of gases very greatly. The question arises: is there some suitable blood chemical which changes appreciably only in asphyxia and not in any other manner of death? And does it maintain its levels after death too? If such a chemical – which till now has remained elusive – could be found, it would become very easy for forensic pathologists to diagnose asphyxia. This is exactly what Sawaguchis have tried to do.

Let us learn something more about asphyxia. Three types of asphyxia are then defined according to the clinical course. Acute asphyxia is said to occur when the time interval between the onset of asphyxia till death ranges from a few minutes to a little over ten minutes. Typical examples are hanging, complete ligature strangulation, and complete airway closure by any other means. In subacute asphyxia the duration of survival is more than ten minutes as in incomplete airway closure or airway narrowing and delayed death from drowning. Asphyxia of a still longer duration (typically between 50 and 183 minutes) results in adaptive and compensatory responses. This is known as chronic asphyxia. All their work has to be seen in the context of these definitions.

Let us now have a look at the kind of work Sawaguchis have done. They have taken rabbits and dogs and have asphyxiated them experimentally in a number of ways. Why rabbits and dogs, and not other animals? An animal had to be chosen, that could withstand the experimental conditions without anesthesia, and rabbits seemed to suit the bill very well. Dogs were chosen for a selected number of purposes only - as for the estimation of blood sugar after asphyxia - because “antibodies may be used in these animals for insulin analysis related to carbohydrate metabolism”.

Six different methods were employed to asphyxiate these animals and various blood constituents studied after that. The methods were (i) Pressure on the windpipe (known technically as trachea) (ii) Asphyxiator (iii) Tracheostenotic cannula (iv) Hanging (v) Strangulation and (vi) Compression of nerves and blood vessels. In addition a control group was killed by four different methods - by cyanide, strychnine, air embolism (introducing air bubbles in blood vessels) and by blows to the neck. Of these the strychnine group gave several findings similar to those of asphyxia, as strychnine in large amounts is known to paralyze the respiratory center in the brain and this effect can be construed as equivalent to asphyxiation.

In the first group the pressure on the neck was not applied directly. Instead, by an elaborate surgical procedure the trachea of the animals was exposed which was then occluded by applying pressure with a pair of haemostatic forceps. Asphyxiator is an interesting device, which mimics a closed room. For the rabbits, this was an airtight box measuring 25x40x25 cm (capacity 25 L) and made of clear resin, and for the dog it measured 30x60x30 cm (Capacity 54 L). It could be hermetically sealed by attaching highly elastic rubber pieces to the sections where the main body and its cover came in contact. The typical survival time for the animals in this box was about 2 to 2.5 hours, which mimicked chronic asphyxiating conditions in a closed room.

Tracheostenotic cannula is again an extremely interesting device (and something of which I for one, heard for the first time!). It is a tube which can be inserted in the trachea. The tube can be surgically inserted in the trachea in such a way that the little nozzle juts out (please refer to accompanying figure). The tube has a small stenotic portion which is about 3.0 mm long and just 0.5 mm wide. To the nozzle can be attached a small vinyl bag (see the figure below) through which 3,400 to 5,000 ml of air could be delivered in strictly measured quantities. Things could be so arranged, that the animal could be made to breathe either through the nose - in which case, it had to overcome the resistance of the stenotic part of the cannula, although the supply of air remained unlimited - or through the vinyl bag - in which case there was no resistance, but the supply of air was limited. As can easily be seen, while the latter case simulates locking up in a room, the former corresponds more to conditions like hanging and strangulation. The typical survival period in the latter (in which the animal was made to breathe from air in the vinyl bag) was less than 60 minutes, while in the latter case it was between 50-183 minutes. In this way, the authors could produce conditions of subacute and chronic asphyxia.

In addition, some animals were hanged and others strangulated. Details of strangulation are provided by Sawaguchis in their book, which they have written to describe their experiments. Two synthetic resin ropes measuring 0.5 cm in diameter were wrapped round the neck once and pulled from both ends with a traction force amounting to 2.5 to 3.5 times the body weight (the traction force is an important parameter in strangulation. In hanging, it is necessarily equal to 1).

Then there is a last group of animals in which the death was caused by compression of major blood vessels and the nerves of the neck. This was also achieved by first exposing these structures by an elaborate surgical procedure and then directly clamping them.

What about the results? Well, they are as interesting as can be. The authors have studied an amazing array of biochemical markers including serum proteins, glycoproteins, serum enzymes and isozymes, blood sugar, hormone levels, and blood lipids. Other things studied are the dynamics of body fluid and acid-base equilibrium, serum electrolytes, blood gases, CSF gases and acid-base equilibrium and partial pressures of the gases contained in the brain, liver and kidney tissues.

The details of results are not relevant for the authors. But what is interesting that the authors indeed found that asphyxia changes the levels of certain chemicals in our blood. For instance, the authors found that the serum total protein level rises immediately after lethal asphyxia which they ascribe to “condensation of the blood during the asphyxial process”. Although the total protein rises, there is a reduction in the alpha-1 and gamma globulin fractions and increases in the albumin fraction and alpha-2 and beta globulin fractions. The authors ascribe the increase in the albumin fraction to the “escape of blood components as a consequence of acidosis .. and damage to the vascular wall”. Similarly they found an increase in calcium in asphyxial deaths, especially those due to strangulation, and this they ascribe to the pressure on the parathyroid gland! The readers need not worry about the technical language. But what should interest the readers is that now there could be a way by which perhaps forensic experts could just tell the cause of death by asking for blood examination.

So are we moving towards an era, where in doubtful cases, a pathologist could just order a few routine blood tests (of the corpse) and write out the cause of death? Well, we will have to wait and see, but what I definitely can say, that about a century ago, one would have refuted this assertion vehemently in relation to clinical diagnosis. At that time the quartet of inspection, palpation, percussion and auscultation was the holy grail of correct diagnosis, but how many clinicians routinely employ it today. They are just happy to order blood tests, X-rays and other investigations at the drop of a hat without an iota of doubt that they will miss out much. Who knows forensic pathology may reflect this state of affairs a century hence.

Captions to figures:

001.jpg: Organs of the neck and test sites. 1. Site where the windpipe is obstructed 2. Site where a canula or probe is installed for insertion into the major artery of the neck - the carotid artery

002.jpg: Tracheostenotic Canula (designed by the Japanese worker Akiko Sawaguchi and Toshiko Sawaguchi)

003.jpg: Asphyxia experiment using a vinyl bag. 1. Tracheal canula attached here 2. Commercially available small vinyl bag 3. Oxygen monitor attached here

004.jpg: This is how the instruments are fixed in the dog.

This article has (2038) words

Dr. Anil Aggrawal, M.D.

Professor of Forensic Medicine

Maulana Azad Medical College

New Delhi‑110002