Firearm Identification: Scientific Equipment PDF

## Chapter II: Scientific Equipment Used in Firearm Identification ### Learning Objectives: At the end of this chapter, the students will be able to: 1. Recognize the different equipment used in Firearms Identification. 2. Know the functions of each laboratory equipment for Forensic Ballistics. 3...

## Chapter II: Scientific Equipment Used in Firearm Identification ### Learning Objectives: At the end of this chapter, the students will be able to: 1. Recognize the different equipment used in Firearms Identification. 2. Know the functions of each laboratory equipment for Forensic Ballistics. 3. Apply the knowledge on the proper use and care of the different laboratory equipment. ### Introduction By means of this equipment and with qualified men to use them, the police will be more effective in their drive against crimes involving firearms. At times, an insignificant fired bullet or shell found at the crime scene will serve as the only "missing link" in the final solution of a crime wherein a gun has been used. And this is brought out to light only in the laboratory by the use of different equipment. It includes: ### Bullet Comparison Microscope It is designed to permit the firearm examiner to differentiate two fired bullet or shell, by simultaneously observing their magnified image in a single microscopic field. Fired bullet and shell are examined and compared in either INTERMARRIAGE (half of the same image of the evidence bullet/shell and half of the same image of the test bullet/shell of the same direction, the same magnification, and the same level or plane are merged into one image to look for the congruency of stations or the same markings) and JUXTAPOSITION (critical side by side comparison at the same time, direction, magnification, image and level or plane to find the same feature, structure of striations to the specimens under observation). The forensic examiner can take photomicrographs which are needed for: court presentations as an exhibit to support the ballisticians’ findings he observed under this instrument. The photomicrograph will give a clue to the judge how the ballistician arrived with his findings and conclusions. It was introduced by Dr. Calvin H. Goddard in April 1925. He was the first to own and used the first bullet comparison microscope, and through his efforts, he is considered as the father of modern ballistics. ### Stereoscopic Microscope It is generally used in the primary examinations of fired bullet and shells to determine the relative distribution of the class characteristics or for orientation purposes. It can also be used in the closed-up examination of tampered serial numbers of firearms. In the middle of the 19th century, Francis Herbert Wenham of London designed the first successful stereomicroscope. The first modern stereoscopic microscope was introduced in the United States by Cycloptic. ### Shadowgraph It contains a series of microscopic lenses of different magnifications that can be used in examining fired bullets or fired shells to determine the class characteristics and also for orientation purposes. This instrument contains a large circular ground glass, and a diameter about 14 inches, wherein the observation and comparison of class characteristics are done similarly with the bullet comparison microscope. ### CP-6 Comparison Projector Similar to bullet comparison micro-scope, in which two fired bullets of the shell can be compared simultaneously by projecting the image on a large screen and is observed at a vertical and comfortable viewing. The instrument was invented by William Howard Livens, an engineer and British army. ### Bullet Recovery Box It used to obtain test fired bullets or test fired shells for examination and comparison to the questioned bullets or shell. Several designs of bullet recovery box are now adopted, for as long as it could meet the desired result in test firing and retrieved the fired bullet undamaged. This is commonly filled with cotton but sometimes water tank, sawdust with oil, sand, waste threads, darak, banana trunks or rubber strips can be used and separated by cardboards. ### Micrometer/Caliper This is used in making measurements such as bullet diameter, bore diameter, barrel length and other important details. ### Analytical or Torsion Balance Used for determining weights of bullets or shotgun pellets – for possible determination of type, caliber and make of firearms from which fired. ### Onoscope A small instrument that is sometimes used in examining the internal surface of the gun barrel with a tiny lamp at the terminal portion and this is inserted inside the bore for internal examination. ### Taper Gauge It is used primarily for determining the bore diameter of firearms. ### Scanning Electron Microscope A high-powered electron microscope used to identify left over particles like gunpowder residues and primer residues. This is a computer system combined with an electron microscopeandlaserspectrophotometry unit. Its power is so great that with a mere speck of dust it could identify the elemental components of the particle under examination. ### Chronograph It is used to measure the speed of the bullet. It was invented by Alfred Lee Loomis in 1918. ### Bullet Puller It is used to separate the bullet from the cartridge case. ### Electric Gun Marker/Stylus Used in the laboratory for marking fired bullets, fired shells and firearms submitted for examination. ### Filar Micrometer Eyepiece A measuring microscope to read the width of the land and groove marks and to obtain the pitch of the rifling in turns per inch. ### Helixometer It is used in measuring the pitch of riflings of firearms. This instrument is generally used in highly advanced ballistics laboratory. With this instrument, it is possible to measure the angle of twist in a rifled pistol or revolver barrel. It is used in inserting the telescope and aligning it with the axis of the bore. The scope is mounted in a rotatable bearing, with a graduated disc which permits reading circular measurements to three minutes of an arc. This instrument was invented by John H. Fisher. ### Computerized Comparison Microscope It is similar to the bullet comparison microscope; the only difference is the magnified image that is seen in the monitor. It is more convenient to use than a manual one. ### Basic Parts: - **Monitor** - screen through which the magnified image from the microscope may be viewed - **Central Processing Unit** - the brain of the computer where all programs and process are installed - **Automatic Voltage Regulator** - regulates the supply of power to the system of the machine - **Mouse** - a palm operating device used to interact with the interface of the program. - **Keyboard** - a computer peripheral used in encoding data to the computer - **Switch** - used to turn on and off the lights of the machine - **Condenser** - concentrates the light on the specimen - **Camera** - transfers the image of the microscope to the computer system - **Magnification Knob** - adjusts the size of the magnified image of the specimen as viewed in the monitor - **Body** - carries the lens and camera systems and permits them to be moved in relation to the specimen for focusing - **Stage** - the platform where the specimen is placed for magnification - **Focusing Knob** - makes focal adjustments based on the selected magnification - **Centering Knob** - moves the stage so that the mounted specimen may be properly viewed in the monitor.