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introduction to forensic ballistics

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introductory information related to the field of firearms identification; the evidences, the principles involeved in their examination and the categories of guns.

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introduction to forensic ballistics

  1. 1. INTRODUCTION TO FORENSIC BALLISTICS
  2. 2. CONTENT 1. INTRODUCTION TO BALLISTICS -forensic ballistics and its applications - History of forensic ballistics 2. FIREARMS AND ITS BASIC PARTS -Types of firearms -Basic parts 3. AMMUNITION 4. PRINCIPLES IN FIREARMS IDENTIFICATION - Class characteristics -Individual characteristics REFERENCES
  3. 3. 1. INTRODUCTION TO BALLISTICS Man has always been fascinated with the use of weapons, including those which propel any substance of any form towards the desired target.Earliest known projectiles were arrows, stones or splints that may or may not have been propelled by a bow or a catapult. This fascination and curiosity gradually lead to the field of ballistics. Ballistics is a field in mechanics that deals with the study of the launching, flight behaviour and effects of the projectile on the target. It is also deals with the design in the projectile and its acceleration in order to achieve the desired performance. Ballistics is divided into three types: Internal ballistics- deals with the launching of the projectile, that is, upon ignition or expansion of compressed air until the projectile reaches the muzzle. External ballistics- it deals with the flight behaviour of the projectile that is, the effects of air, wind or any other medium through which the projectile travels after its launching. Terminal ballistics- it deals with the effects of the projectile upon impact on its target(including intermediary targets).
  4. 4. FORENSIC BALLISTICS AND ITS APPLICATION Forensic ballistics is the application of the principles of ballistics in legal situations so as to maintain law and order. It includes: -collection and examination of projectiles of guns and guns -toolmark analysis -study of bullet wounds (here the forensic pathologist incorporates terminal ballistics while examining wounds on the corpse). Forensic ballistic is also known as firearms identification since it aids in determining the weapon of offence through examination of the projectile it supposedly fired.
  5. 5. Firearms identification aids investigators in criminal investigation relating to cases like homicide, assault, robbery, burglary, mob violence and violence related to police encounters. This field can help us determine: -whether the crime that took place was accidental, suicidal, negligent or intentional -the number of shootings during that event and if more than one person was involved. -the sequence of occurrence of the events. -the distance between the target and the shooter. -the type of weapon used in the commission of the crime. The field of ballistics in criminal investigation has been useful in solving varieties of many cold blood cases as it also includes tool mark analysis in order to determine the type of weapon used in the commission of the crime. Also the condition of the wound can tell a lot about the nature of the weapon used.
  6. 6. HISTORY OF FORENSIC BALLISTICS 1493-1508- Emperor Maximilian of Germany proposed rifling of guns in order to impart rotatory motion to the projectile during firing. However the fact that rifling marks on the projectile could aid in identification of the weapon that fired it was not recognized until the 19th century. 1835- Henry Goddard of the Bow Street Runners examined the bullet from the crime scene and noticed a defect on it. On comparing the mold found in the suspect's home to the defect on the bullet a positive comparison was made which lead to the conviction of the suspect. Bullets those day were made by pouring lead into a mold. 1860- In the Regina vs. Richardson case the evidence included a newspaper wadding used to seal the bullet from the gunpowder. The wadding was found on the victims wounds which contained The London Times paper of March 27th 1854. The same material of the same paper was found in the suspect's home. The comparison of these two samples lead to conviction of the suspect.
  7. 7. 1902- Oliver Wendell Holmes turned to magnification on account of increased firearms manufacture which lead to standardization of rifling. 1912- Professor Balthazar used photography to document circumferences of the bullets found at the crime scenes and those test fired. 1925- Charles E. Waite along with Calvin Goddard, Philippe Gravelle and John Fischer founded the Bureau Forensic Ballistics in New York. Gravelle developed comparison microscope and Fischer invented the helixometer. Calvin Goddard became known for his identification work in the Sacco and Vanzetti case. Fig: Calvin Goddard examining the barrel of a revolver using a helixometer.
  8. 8. 2. FIREARMS A firearm is a mechanical device adapted to hurl a projectile into air or any other medium by the action of explosive forces or any other forms of energy. The earliest known firearm was a firelance used by the Chinese during the 10th century A.D.(in the figure, a Chinese firelance used to fire either an arrow or a group of solid projectiles). According to the Indian Arms Act 1959, a firearm is a device of any description that is adapted to hurl projectile or a group of projectiles of any form or design by the action of explosions or any other form of energy. The first drawing of the most primitive form of the gun was made in the 14th century.
  9. 9. BASIC PARTS OF A FIREARM Gun is a type of modern firearm made out of predominantly steel. The basic parts of a gun are: Stock Action Barrel Stock is the part that holds other parts of the firearm on place and is even used as support by the shooter during firing. It is also a safety feature while handling guns. In semiautomatic and automatic guns it is called as a magazine. Action is the mechanism for loading, unloading, ejecting and extracting the ammunition. Barrel is a metallic tube through which the projectile travels upon firing and it provides space for the expansion of gases. It may be rifled or smooth on its inner surface.
  10. 10. CLASSIFICATION OF FIREARMS Studying the classification of firearms is useful especially when it come to determining the type of gun used in the commission of the crime. Firearms are classified into: Single shot- in these type of firearms the gun has to be loaded every single time after every shot. Many shotguns come under this category. Repeaters- in this type of firearm, manual loading or sometime extraction of the ammunition has to be done after each shooting takes place. Examples are revolvers and some rifles. Semi automatic- in this type automatic extraction and ejection of the spent cartridges and loading of live cartridges take place after each shooting as long as the trigger is pulled. For the next shooting the trigger is released and again pulled to repeat the entire process. Automatic- this type is similar to semi automatic guns except that as long as the trigger is pulled automatic loading, extraction and ejection of the cartridges occurs repeatedly provided that the magazine is not exhausted. Examples include machine submachine guns.
  11. 11. A REPEATER REVOLVER A SEMI AUTOMATIC PISTOL(9MM)
  12. 12. A SUB MACHINE GUN( AUTOMATIC) A SINGLE SHOT PISTOL(BREECH LOADING)
  13. 13. The firearms can also be classified based on the positions of where the ammunition is loaded. They are: Breech loaders Muzzleloaders Magazine loaders Also rifles are classified into: Pump action Bolt action Break action Lever action Automatic Rifles are firearms with a long barrel length with a rifled bore. Firearms are also classified into: Handguns- example: revolvers, self loading pistols Shoulder guns- example: rifles Improvised firearms are those guns which do not resemble a typical gn but are made from the available materials(in fig).
  14. 14. Classification of firearms based on their inner barrel surface or bore RIFLED BORE .These are characterized by the presence of furrow portions that alternate each other. These depressions or furrow like portions are known as grooves and the raised portions between them are called lands. They are arranged in a spiral manner. . The motion of the projectile that travels through the bore and then .in these type of firearms, bullets are used. . The measurement for the bore is caliber(distance between two diagonally parallel grooves). .Absence of choke SMOOTH BORE These are characterized by the absence of lands or grooves. The cross section of the bore is circular at any point. The projectiles travel in a forward motion and the range is very much less. . In these type of firearms pellets, slugs or shots are used. .the measurement for the bore used is gauge or bore diameter. .presence of choke
  15. 15. Rifled bore(below) and smooth bore of two war cannons.
  16. 16. 3. AMMUNITION Ammunition means anything that contains a projectile and a propellant. In a broad sense it can mean materials used for combat or war and these include grenades, missiles, riot pistols, explosives etc. Its short form is ammo. It is derived from the French word 'la munition which means material used for war. A single unit of ammunition for a gun is equivalent to a single live cartridge. A cartridge is a metallic enclosure consisting of the projectile, primer and the propellant. It is made up of metal or plastic.
  17. 17. Components of a cartridge A cartridge has basically four components: Primer- it is a friction or impact sensitive material primarily made up of a fulminate of mercury. Propellant- it is of two types; gunpowder or smokeless powder. Gunpowder is a primitive type of propellant. It produces a lot of residues upon firing and this can corrode the quality of the gun.it is made up sulphur, charcoal and potassium nitrate in the ratio 10:5:85. Smokeless powders are made out of nitrocellulose and nitroglycerin. (in fig. A rifled cartridge with a flat nosed bullet) .
  18. 18. Projectile- it is located on the anterior end of the cartridge.it can be pellets, slug or shot(in case of smooth bore guns) or a bullet in case of rifled guns. Cartridge case- they are used to hold the components in place. They have been made up of steel, aluminum, copper and brass. Brass is the most durable. Wads- these are either made up of plastic or cardboard. They are found in shotgun cartridges where they ensure separation between the pellets and the powder.
  19. 19. Rifle cartridge shotgun cartridge
  20. 20. 4. PRINCIPLES IN FIREARMS IDENTIFICATION The principle that no two firearms even of the same make and model made one after can impart identical marks onto the bullet being fired from it is similar to the thumbprint we apply for fingerprints. When a bullet is fired from the gun, marks get imprinted not only on the bullet but also onto the cartridge case. These marks are produced by the parts of the firearm. They are: Firing pin- the marks produced by the firing pin onto the cartridge case are very significant in identification of the suspected weapon. Breech face- the area surrounding the firing pin hole is the breech face. During firing when the cartridge case is pushed onto the breech face where the marks get imprinted onto the backside of the cartridge case.
  21. 21. Chamber- the area where the ammunition is inserted(in case of breech loading firearms). Usually this part is insignificant in context to identification since the diameter of the chamber is greater than those of the bullet and the cartridge case separately. Extractor and ejector- these parts of the firearm come in contact with the cartridge cases. Leed- It provides slippage marks onto the bullet when the bullet travels form the chamber to the barrel during firing. In fig- firing pin indentations on the base of a rifled cartridge observed through microscopy.
  22. 22. Class characteristics include the bore diameter of the firearm, the angle of twist of the lands and grooves, the direction of twist of the lands and grooves and the width of the grooves and lands. These characteristics help us to narrow down to guns of the same make and model. Individual characteristics are the finer imperfections of the indentations produced by the firearm. These help us find the specific firearm. These imperfections are due to manufacturing, use of the weapon and corrosion of the weapon. in fig. Striations produced on the cartridge case due to chamber.
  23. 23. Marks on the test cartridge(left) compared with those of the questioned cartridge using a comparison microscope of 20x.
  24. 24. References Heard, B. (2008): Handbook of firearms and ballistics, Examining and interpreting forensic evidence( 2nd edition, Wiley) ,416 pages. Rao.M.S., Maithil.B.P., Kumar.S(2009): Crime Scene Management, A Forensic Approach(1st edition, Selective and scientific books), 439 pages.1st edition. Maithil.B.P. (2012): Physical evidence in crime scene investigation, The silent witness(5th edition, Selective and scientific books), 432 pages.

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