SUBJECT FORENSIC SCIENCE Paper No. and Title PAPER No. 6: Forensic Ballistics Module No. and Title MODULE No.17: Terminal Ballistics - Part I Module Tag FSC_P6_M17 FORENSIC SCIENCE PAPER No.6: Forensic Ballistics MODULE No.17: Terminal Ballistics- Part I TABLE OF CONTENTS 1. Learning Outcomes 2. Introduction 3. Penetration Potential 4. Concept of Wound Ballistics 5. Target Site 6. Identification of Entry Wound 7. Yaw and Wounds 8. Velocity of Missiles & Wounds 9. Constructional Features & Wounding Capability 10. Summary FORENSIC SCIENCE PAPER No.6: Forensic Ballistics MODULE No.17: Terminal Ballistics- Part I 1. Learning Outcomes After studying this module, you shall be able to know about- What is Terminal Ballistics What is penetration potential and the concept behind wound ballistics You will be also made familiar with the identification of entry wounds and the constructional features and wounding capabilities 2. Introduction Ballistics is the science involving study of motion of projectiles. The term Ballistics is derived from the Latin word “Ballistic” meaning a cross-bow like device for throwing stones by means of twisted ropes. When firing pin hits the primer, excessive heat is generated and the bullet (projectile) get pushed from the cartridge and start moving inside the barrel of a fire arm. This comes under the field of internal ballistics. The study of internal ballistics involves burning or combustion of grains of the propellants. The study is called internal ballistics so long as motion of projectile is inside the barrel of the weapon. As soon as the projectile leaves the muzzle end of the weapon the External ballistics comes into play and remain till the projectile hits the target. It covers the study of the path of the bullet from the muzzle of the weapon to the target. It involves parameters such as bullet shape, density, resistance of air, atmospheric conditions, drift of the bullet and its stability as well as rotation of earth. The role of external ballistics ends once the projectile (or projectiles) reaches the target. Terminal ballistic deals with behavior of the missile (projectile) once it hits the target. Terminal ballistic is the study of penetration of missile in deferent types of target such as solids as well as liquids. It is the study of wounding capabilities in animal tissues. It involves the studies of bullet resistance materials such as jackets and vests. The study involves penetration of bullets in making holes in glass panes in windows, showcases and buildings. The target may be soil, brick or wood. FORENSIC SCIENCE PAPER No.6: Forensic Ballistics MODULE No.17: Terminal Ballistics- Part I If the target is human body, the Terminal Ballistics may be called Wound Ballistics. This is an important aspect of terminal ballistics since, deferent parts of human body react differently to similar caliber missile with same velocity. Broadly speaking terminal ballistics sub- divided into penetration potential which is the capability of a missile to penetrate various material and wound ballistics which is the effect the missile has on living tissues. Both of them are surrounded with misinformation and need to be discussed. 3. Penetration Potential The penetration of different material could be of great value while investigating gunfire cases. In order to assess the performance of bullet and cartridge penetration of pine board of various thickness are carried out. The test was however been found to be of no help as it’s full of inaccuracies due to several factors mentioned below. (i) Moisture content (ii) Knot content (iii) Age of the tree (iv) Separation of boards gave variable result. To penetrate human skin, 0.177” lead air gun pellet requires as minimum velocity of 300fps, whereas, 0.22” lead air gun would penetrate human skin if the minimum velocity is 2.50fps. In case of glass, 0.22” lead air gun pellet will make a hole when its velocity is 450fps but is unable to penetrate ¼” glass plate. To penetrate ¼” glass plate minimum required velocity is 650 fps. FORENSIC SCIENCE PAPER No.6: Forensic Ballistics MODULE No.17: Terminal Ballistics- Part I 4. Concept of Wound Ballistics Wound ballistics basic concepts there are three concepts generally held by most as to the effect of a bullet striking a human being. The bullet dampens its way through having a small entry hole and equally sized exit hole. Another concept is that if someone is shot by any firearm (other than air rifle) the impact would be sufficient to leave him off his feet to fly through the air. None of the above is a correct concept and is incorrect in one way or the other. One of the reason is that the bullet when passing through human tissue will impact will consume some or all of its kinetic energy to the surrounding tissue resulting in throwing the tissue away from the bullets path in a radial manner leaving a temporary wound cavity which has much large diameter than the diameter of the bullet. The temporary nature of this cavity results from the natural elasticity of the human skin which regains its original structure after the bullet has passed which is shown in the figure below. Fig.1: Permanent and Temporary cavity FORENSIC SCIENCE PAPER No.6: Forensic Ballistics MODULE No.17: Terminal Ballistics- Part I There is also a permanent cavity (as shown in the above figure) resulting from the destruction of tissue caused by the bullet itself. The permanent cavity is dependent on the cross sectional area of the bullet and any secondary missiles produced due to break up the bullet during its passage. Temporary cavity has a very short life span as the name indicate and is followed by a number of aftershocks decreasing in severely. The final, permanent cavity may be many times greater than the diameter of the missile, but is also many times smaller than the temporary cavity. Unlike the temporary cavity, where the tissue is merely being thrown away from the wound track and no permanent damage is being caused to the tissue. The permanent cavity is caused by the actual destruction of the tissue by the passage of the bullets. The dimensions of the temporary cavity are dependent upon the shape, weight, size and velocity of the projectile as well as the elasticity of the surrounding structures. 5. Target Site A human body is not a uniform medium. It has about 80% water. The water is not uniformly distributed. At some places there are bones, at other places, veins, nerves, muscles or blood vessels. Thus the vulnerability is unevenly distributed. The minimum velocity required to penetrate the skin is about 40-50 meters per second. This is known as Threshold Velocity. Its value for bone penetration is 60 meters per second. Wounding effect of a projectile will depend upon: The target site whether it is front side or back side of the body. The head injury would differ from the wound found on the waist. The velocity of the projectile. The constructional features. The range of firing. A contact injury would obviously be different from a distant shot injury. FORENSIC SCIENCE PAPER No.6: Forensic Ballistics MODULE No.17: Terminal Ballistics- Part I There is a misconception that entry hole is always small and exit hole is large. Perhaps, it is a major factor during interpretation of close range or suicide wounds is called for. When a handgun is held with the muzzle in tight contact with the skin the entry hole can be massive. The high pressure gases following the bullet out of the barrel have nowhere to go other than into the wound carved by the bullet. The gases expand at a rate greater than the speed at which the bullet is passing through. Since the tissues have nowhere to move except bursting back out through the bullet entry hole which can be enormous and may give indication of an exit wound but it is incorrect. It is correct is say that velocity plays an important role in creating injuries but there are other factors which may result in making more serious injuries. It is correct to state that the relation of energy with velocity. However, it does not tell the truly. For instance, when the Mark VI .303 bullet could not stop the Afghans, the British used Dum Dum bullets which were caused extensive wounds inspects of the fact that Dum Dum bullets had less energy than the standard Mark VI .303 bullets but were found super in causing serious injuries. The injury created on a particular part of the body is responsible for the extent of shock if a projectile cuts the skin only. It does not do much harm. In the same manner a projectile hitting a finger would not create much of a shock. When a shot injuries the brain, the heart, the spinal cord or other vital organs like aorta, enough shock is created resulting in serious consequence of fatal injuries. It is against this background that the elephant hunters try to reach the brain of the game through the area in between the ear and eye of an elephant for target area though it is a small circle of diameter about four inches only. In this connection it is further mentioned that the most powerful elephant rifle ever commercially produced would have no stopping on an elephant running at about 20 miles per hour. FORENSIC SCIENCE PAPER No.6: Forensic Ballistics MODULE No.17: Terminal Ballistics- Part I 6. Identification of Entry Wound Identification of entry wound can be done by the presence of partially burnt propellant in the wound and blood & tissue in or upon the barrel of the weapon will correctly identify the wound as an entry rather than an exit wound.