Sitting Bull

 

The nature of firearm wounds varies considerably with the  type of weapon employed. A general knowledge of the  main features of the various types of gun in common use is  essential, though there is no need for the pathologist to  master the unnecessary mass of detail on firearm construction. Indeed,  much of this is solely the province of the firearms examiner,  not the doctor. The inordinate amount of detail sometimes  provided is perhaps symptomatic of the fascination which  firearms hold for many men - women.

 

In the context of wounding, guns are of two main types.

The smooth-bore weapon or 'shotgun'

A shotgun consists of one or more metal barrels of relatively  wide diameter, which are smooth on the inner surface. They  fire a variable number of spherical lead shot (pellets), which  emerge from the end (muzzle), from where they gradually  diverge in the form of a long, narrow cone. Exceptionally, a  shotgun may fire a few large projectiles or even a single slug,  but these are rarely met with in forensic practice, the usual  load of pellets totalling scores or hundreds. Special types of  projectile are described later. A shotgun often has two barrels, either side by side or 'up-and-under'. One barrel may be  parallel sided (the 'cylinder') and the other slightly tapered  towards the muzzle (the 'choke'). The latter will produce a  narrower cone of shot and this affects estimates of range  derived from the size of the wound. There are several gradations of choke, such as 'improved cylinder', 'modified choke', 'half-choke' and 'full-choke'. Some modern weapons have the facility for removing one particular type of barrel and replacing it with another degree of choke. Modern accessories can convert a cylinder barrel to a choke barrel - for example, variable choke such as Poly-Choke, Kutts Compensator and Weaver-Choke.

Shotguns come in two main sizes, which determine the nature of the wound. The first is the 'twelve-bore', usually called 'twelve-gauge' in North America, which has a dia- meter of about 19mm or 0.738 inches. The other is the smaller 'four-ten', usually single-barrelled with a diameter of 10.G mm or 0.410 inches.

 

The ammunition for the shotgun is a cartridge made of a cardboard or plastic cylinder fitted into a metal base. This carries a percussion detonator that is struck by the spring- loaded firing pin when the trigger is pulled. The cartridge contains a charge of propellant, above which are 'wads' or pistons of felt, and cardboard or plastic discs, or both. Above these is the charge of shot, which varies greatly in number and size, finally covered by a card or plastic disc. This description is of the old, classical cartridge but modern ammunition has a variety of devices incorporated into the cartridge to improve efficiency and accuracy. These include the Power Piston, a proprietary name for one of a class of cartridges which holds the shot inside a polythene cup and which itself may contribute to the wound at short range. Other modern cartridges may have plastic granules as a filler between the shot; this brightly coloured material may be found inside the wounds. Tampering with the contents of cartridges may markedly alter the spread and other characteristics of the shot and hence the resulting wound. The shot may be fused into a mass by pouring paraffin wax or even molten pitch into the cartridge. The cardboard or plastic cylinder may be partly cut through at the level of the wads, so that, on firing, the upper part of the casing is blown out to restrain the divergence of the pellets.

The variety of types of rifled ammunition is even greater than the range of weapons designed to fire them, but all conform to a general pattern. There is a metal cylinder, closed at one  end, which is the 'shell' or cartridge, carrying a percussion  detonator in the base, either centrally or peripherally. The shell is loaded with explosive propellant such as nitrocellulose  and the bullet is firmly clamped into the open end. The bullet may be composed of a variety of metals, often compound.  A lead core may be covered in a nickel or steel jacket, but  there are many other variations. The detonator may contain elements such as barium, bismuth mercury or antimony.  Both shotgun and rifled weapon ammunition have a common purpose when detonated - to produce large volumes of hot gas under pressure that expel the bullet or shot from the barrel. One gram of black powder produces about 3000 ml and nitrocellulose produces some 13 000ml of gas, which consists of carbon dioxide, monoxide, nitrogen, hydrogen sulphide, hydrogen, methane and many other substances, all at high temperatures.

Though the construction and performance of weapons is of vital interest to the forensic firearms examiner, the relevance to the pathologist is concentrated in those aspects which affect the nature of the wound:

-          whether the weapon is smooth-bore or rifled;

-          if rifled, the muzzle velocity of the weapon;

-          the nature of the projectile(s);

-          the nature of the propellant;

-          the degree of choke, if any;

-          the range of discharge;

the angle of discharge

The following constituents of the cartridge emerge on the discharge of a shotgun and all may contribute to the wound:

-          lead pellets;

-          soot in the form of smoke and debris;

-          unburnt and burning propellant particles;

-          flame and hot gases under pressure;

-          carbon monoxide;

-          wads - either felt, cardboard or plastic;

-          detonator constituents;

-          fragments of the cartridge case.;

When a shotgun is fired, a compact mass of shot emerges from the muzzle and then begins to disperse, the divergence increasing progressively as the distance lengthens. A tongue of flame and hot gas follows the shot. High pressure and temperature exists just outside the muzzle, but this rapidly expands and cools. This gas is composed of oxides of nitrogen, carbon dioxide, hot air and other compounds, but the one of interest to the pathologist is carbon monoxide. Soot from the combustion of propellant is expelled, along with some flakes or grains of propellant that may be still burning. The wads are also expelled, their nature depending upon the type of cartridge. Some modern ammunition may contain other devices that may contribute to the wound. Chemical traces of the elements in the detonator or percussion cap cannot be seen, but may be vital laboratory evidence, where barium, antimony and other metals can be recovered on analysis or by means of the scanning electron microscope. Fragments of the cartridge case may also be ejected, especially if it has been tampered with, as described earlier.

Variation in appearance of a shotgun wound at.increaring range ofdischarge: ](a), split woundfrom contact over bone; I (b), wual round contact wound; 2, close but not contact range up to about 30m (variable); 3, 'rat-hole' woundfrom 30 m to about a metre (variable); 4, satellite pellet holes appearing over a metre; 5, spread of shot increases, central hole diminishes; Q uniform spread with no central hole over about 10m. All these ranges vary greatly with barrel choke, weapon and ammunition.

Where the muzzle is placed tightly against the surface of the abdomen, thorax, limb or neck, the consequent wound will be single and circular, of a size approximately equal to the bore of the weapon, though a .410 wound may be smaller because of the relatively greater effect of elastic contraction of the skin. The edges of the wound may be crenated by individual shot, but usually this feature is not noticeable.

In a tight contact wound, the skin forms a seal around the muzzle, preventing much escape of hot gas and soot, so that soiling and burning are minimal or absent. The recoil, which takes the muzzle away from the skin, may, however, loosen the seal and, if the muzzle is not pressed firmly, flame, gas and soot may escape sideways and affect the skin in the immediate vicinity. Where clothing is interposed between the muzzle and the skin, soot is much more likely to escape sideways and may be found in each layer of fabric, as well as on the underlying skin. The cloth may be singed at the edge of the hole and there may be a ring of burning around the skin wound.

There may be a muzzle impression in a tight contact wound made by firm mechanical pressure or impact of the metal rim against the skin. Many textbooks quite wrongly attribute this to 'recoil', though of course recoil takes the muzzle away from the skin, not towards it. The true explanation of a muzzle mark is either that the assailant physically kept the weapon pressed hard against the skin or - more often - that the sub- cutaneous expansion shortly to be described, lifts the skin forcibly up against the, muzzle. A muzzle mark is a most useful indication to the pathologist of a contact wound. Actual bruising can occur around the muzzle imprint, though this is more likely to be the result of deep contusion from the effects of the blast. Rarely, a double-barrelled weapon may make a ring-like mark adjacent to the entry wound.

Carbon monoxide in the gases combines with haemoglobin and myoglobin to give a pink coloration to the interior of the wound track and adjacent tissues. This diminishes in con- centration along the track, but can still be present in its depths - and even at an exit wound, if there is one. The presence of carboxyhaemoglobin and myoglobin has been advocated as a test for distinguishing the exit from the entrance wound, especially where decomposition has blurred the morphological appearances. This test must be used with caution, though if quantitative measurements are made it can still be a valid exercise.

Acknowledgements:

www.aived.nl    AIVD – @Erik Akerboom ©

www.politie.nl  Politiekorpschef  @Janny Knol©

www.politie.nl WEB Politie - @Henk van Essen©

 

Bibliography:

1.    Criminal Investigations – Crime Scene Investigation.2000

2.    Forensic Science.2006

3.    Techniques of Crime Scene Investigation.2012

4.    Forensics Pathology.2001

5.    Pathology.2005

6.    Forensic DNA Technology (Lewis Publishers,New York, 1991).

7.    The Examination and Typing of Bloodstains in the Crime Laboratory (U.S. Department of Justice, Washington, D.C., 1971).

8.    „A Short History of the Polymerase Chain Reaction". PCR Protocols. Methods in Molecular Biology.

9.    Molecular Cloning: A Laboratory Manual (3rd ed.). Cold Spring Harbor,N.Y.: Cold Spring Harbor Laboratory Press.2001

10.   "Antibodies as Thermolabile Switches: High Temperature Triggering for the Polymerase Chain Reaction". Bio/Technology.1994

11.   Forensic Science Handbook, vol. III (Regents/Prentice Hall, Englewood Cliffs, NJ, 1993).

12.   "Thermostable DNA Polymerases for a Wide Spectrum of Applications: Comparison of a Robust Hybrid TopoTaq to other enzymes". In Kieleczawa J. DNA Sequencing II: Optimizing Preparation and Cleanup. Jones and Bartlett. 2006

13.   Nielsen B, et al., Acute and adaptive responses in humans to exercise in a warm, humid environment, Eur J Physiol 1997

14.   Molnar GW, Survival of hypothermia by men immersed in the ocean. JAMA 1946

15.   Paton BC, Accidental hypothermia. Pharmacol Ther 1983

16.   Simpson K, Exposure to cold-starvation and neglect, in Simpson K (Ed): Modem Trends in Forensic Medicine. St Louis, MO, Mosby Co, 1953.

17.   Fitzgerald FT, Hypoglycemia and accidental hypothermia in an alcoholic population. West J Med 1980

18.   Stoner HB et al., Metabolic aspects of hypothermia in the elderly. Clin Sci 1980

19.   MacGregor DC et al., The effects of ether, ethanol, propanol and butanol on tolerance to deep hypothermia. Dis Chest 1966

20.   Cooper KE, Hunter AR, and Keatinge WR, Accidental hypothermia. Int Anesthesia Clin 1964

21.   Keatinge WR. The effects of subcutaneous fat and of previous exposure to cold on the body temperature, peripheral blood flow and metabolic rate of men in cold water. J Physiol 1960

22.   Sloan REG and Keatinge WR, Cooling rates of young people swimming in cold water. J Appl Physiol 1973

23.   Keatinge WR, Role of cold and immersion accidents. In Adam JM (Ed) Hypothermia – Ashore and Afloat. 1981, Chapter 4, Aberdeen Univ. Press, GB.

24.   Keatinge WR and Evans M, The respiratory and cardiovascular responses to immersion in cold and warm water. QJ Exp Physiol 1961

25.   Keatinge WR and Nadel JA, Immediate respiratory response to sudden cooling of the skin. J Appl Physiol 1965 

26.   Golden F. St C. and Hurvey GR, The “After Drop” and death after rescue from immersion in cold water. In Adam JM (Ed). Hypothermia – Ashore and Afloat, Chapter 5, Aberdeen Univ. Press, GB 1981.

27.   Burton AC and Bazett HC, Study of average temperature of tissue, of exchange of heat and vasomotor responses in man by means of bath coloremeter. Am J Physiol 1936

28.   Adam JM, Cold Weather: Its characteristics, dangers and assessment, In Adam JM (Ed).Hypothermia – Ashore and Afloat, Aberdeen Univ. Press, GB1981.

29.   Modell JH and Davis JH, Electrolyte changes in human drowning victims.Anesthesiology 1969

30.   Bolte RG, et al., The use of extracorporeal rewarming in a child submerged for 66 minutes. JAMA 1988

31.   Ornato JP, The resuscitation of near-drowning victims. JAMA 1986

32.   Conn AW and Barker CA: Fresh water drowning and near-drowning — An update.1984;

33.   Reh H, On the early postmortem course of “washerwoman’s skin at the fingertips.” Z Rechtsmed 1984

34.   Gonzales TA, Vance M, Helpern M, Legal Medicine and Toxicology. New York, Appleton-Century Co, 1937.

35.   Peabody AJ, Diatoms and drowning – A review, Med Sci Law 1980

36.   Foged N, Diatoms and drowning — Once more.Forens Sci Int 1983

37.   "Microscale chaotic advection enables robust convective DNA replication.". Analytical Chemistry. 2013

38.   Sourcebook in Forensic Serology, Immunology, and Biochemistry (U.S. Department of Justice, National Institute of Justice, Washington, D.C.,1983).

39.   C. A. Villee et al., Biology (Saunders College Publishing, Philadelphia, 2nd ed.,1989).

40.   Molecular Biology of the Gene (Benjamin/Cummings Publishing Company, Menlo Park, CA, 4th ed., 1987).

41.   Molecular Evolutionary Genetics (Plenum Press, New York,1985).

42.   Human Physiology. An Integrate. 2016

43.   Dumas JL and Walker N, Bilateral scapular fractures secondary to electrical shock. Arch. Orthopaed & Trauma Surg, 1992; 111(5)

44.   Stueland DT, et al., Bilateral humeral fractures from electrically induced muscular spasm. J. of Emerg. Med. 1989

45.   Shaheen MA and Sabet NA, Bilateral simultaneous fracture of the femoral neck following electrical shock. Injury. 1984

46.   Rajam KH, et al., Fracture of vertebral bodies caused by accidental electric shock. J. Indian Med Assoc. 1976

47.   Wright RK, Broisz HG, and Shuman M, The investigation of electrical injuries and deaths. Presented at the meeting of the American Academy of Forensic Science, Reno, NV, February 2000

48. Broor SL, Kumar A, Chari ST, et al. 1989. Corrosive oesophageal strictures following acid ingestion: clinical profile and results of endoscopic dilatation.

49. Baud FJ, Barriot P, TOGS V, et al. 199 1. Elevated blood cyanide concentrations in victims of smoke inhalation.

50. Blackwell M, Robbins A. 1979. Arsine (arsenic hydride) poisoning in the workplace