TOPIC 7. GUNPOWDER AND OTHER EXPLOSIVES Flashcards
In the investigation of crimes involving the use of firearms, three most important problems may arise. The first and probably of primary importance is the problem of determining whether or not person has fired a gun with bare hands within a pertinent period of time
GUNPOWDER AND OTHER EXPLOSIVES
– because of its inherent defects modern ammunition plants abandoned the use of this.
Black Powder
– is the most widely used propellant. It can either be single base propellant or double propellant.
Smokeless Powder
– possibly the oldest known explosive. It is consists of an intimate mixture of charcoal – 15%, sulfur – 10% and potassium or sodium nitrate 75%. When exploded in open space the following reaction occurs: 2KNO3 + 3C + 3CO2 + K2S + N2
BLACK POWDER
– the most widely used propellant. It is consists of Cellulose Nitrate or Glyceryl Nitrate combined with Cellulose Nitrate and some stabilizers.
SMOKELESS POWDER
– different types of ammunition fired in the same weapon and from the same distance may give different pattern.
Type and Caliber of the Ammunition
– a weapon with 2 inches barrel will deposit residues over a larger area than a weapon having a five inches barrel even though they are fired at the same distance and with the same type of ammunition.
Length of the Barrel of the Gun
– affects the speed with which powder burns. Powder having lesser amount of moisture will burn more rapidly and completely within a given time yielding greater amount of residue.
Humidity
– in high winds the residue will be blown in the directions of the wind yielding a scattered pattern.
Wind Velocity and Direction
– firing vertically, slightly greater than firing horizontally from the same distance. Powder residues have weight. When gun is fired downward o vertically all of the residence will fall on the target, but when fired horizontally some of the residues are likely to fall short of the target.
Direction of Firing
– a test to determine whether a person fired a gun or not with bare hands.
Diphenylamine Paraffin Test or Dermal Nitrate Test or Lunge Diphenylamine Test
– the taking of the cast to extract the nitrates embedded or implanted in the skin.
Paraffin Test
– the chemical aspect of the test. It determines the presence and distribution of nitrates.
Diphenylamine Test
Due to its alkaline character,Ballistolis ideal for cleaning and maintaining black powder firearms. The residues from black powder in chambers and bores are acidic.
Ballistol neutralizes and dissolves them
BLACK POWDER SOLVENT
The leakage of powder is apt to occur when the gun fired is old weapon where the breech mechanism is no longer tightly titled and when the gun used is of the revolver type.
BLACK POWDER SOLVENT
– slight burning
Singeing
– blackening of area around the bullet hole
Smudging
– individual species of nitrates around the bullet hole visible to the naked eye. It is a black coarsely peppered pattern.
Tattooing
– This test is used if the powder particles are deeply embedded.
Walker’s Test