Forensic Analysis of Gunshot Residues (GSR)

Gunshot residues are produced when a cartridge is fired from a firearm. They are also known as firearm discharge residue or powder residues. Gunshot Residue is usually found on hands, clothes, target, on the articles found around the targets, and is also found floating in the air. The gunshot residue is collected in several ways, including the dry and the wet methods. Analysis of gunshot residue is done using different chemical and instrumentation methods. The various methods of analysis using Walker’s test, Greiss test, and instrumentation such as SEM, EDX, and NAA are discussed in this article. GSR analysis is a standard method to determine if a firearm has been used. Particles for GSR analysis typically range from 0.5µ to 10µ. Primer particles containing lead, antimony, barium are detected and analyzed using EDX in Scanning Electron microscopes. Gunshot Residue Examination 1. Visual examination In cases where the firearm is discharged […]

Mechanism of Formation of Gunshot Residues

Gunshot residue, also known as firearms discharge residue, is the residue that gets deposited on the hands and clothing of the victim when a gun is fired. When a gun is fired, especially a revolver, powder residue from the propellant and primer may be blown around the cylinder. Traces of such residues are sometimes transferred to the hands of the shooter. Their location and identification play a critical role in the investigation trials. The absence of GSR can also provide valuable information. GUNSHOT RESIDUES GSR is the unburnt particles, gases, and non-volatile substances coming from primer, propellant, bullet, and firearm. Gunshot residue consists of organic as well as inorganic components. Organic compounds present are mainly from the primer and the propellant such as nitrocellulose, lubricants used for lubrication of bullets, nitro-glycerine in the case of double-base propellants, and organic materials such as plasticizers. Inorganic components from the primer and propellant […]

Forensic Examination of Bullets & Cartridges

Forensic examination of a firearm is the process of examining the various characteristics of firearms, bullets, and cartridges left behind at the crime scene. Specialists in this field are often tasked with linking bullets and cartridges to the weapons and the weapons to the individuals. The various characteristics such as breech face marks, firing pin marks, extractor & ejector marks, size of the bullets, striations found on bullets are compared with the test-fired cartridges and bullets. Comparison is made simultaneously between the questioned samples and the test-fired samples using a comparison microscope. Cartridge Case Examination The examination of cartridge cases depends on the unique marks left by various parts of the firearms that include the following: Breech Face Marks:- These marks come from the area surrounding the firing pin of the gun. After the propellant powder is ignited by the firing pin striking the primer cup, tremendous pressure is exerted in […]

Firing Mechanism of Different Firearms

The firearm is defined as a device by which a projectile or projectile can be hurled with an excellent force. The modern firearm is classified based on several characteristics. Firing mechanisms involve the process such as loading of ammunition, chambering, locking, firing, unlocking, extracting, ejecting, and cocking. This article further deals with the various stages involved in the firing mechanism. Cycle of Operation of Firearms FEEDING Feeding places around within the receiver just to the rear of the chamber. A spring-loaded follower accomplishes feeding in the magazine. CHAMBERING This action is required to ram a fresh round into the chamber. The cartridge is now aligned into the chamber part of the barrel. LOCKING Locking holds the bolt in its forward position for a brief period to avoid the loss of pressure until unlocked by other forces. FIRING  Firing occurs when the pin or the striker strikes the primer of the cartridge. […]

Synthesis And Characteristics of TNT, PETN & RDX

A detonator is a small explosive device that is used for detonating high explosives. The synthesis of explosives helps produce new substances for research and development. Eack of the explosives has different characteristics. TNT, PETN and RDX are explosives that are highly encountered by police. These are high-power military explosives that fall under the category of secondary high explosives that do not easily detonate by flame heat or friction. Therefore, knowledge of the synthesis and characteristics of these explosives helps law enforcement agencies protect and safeguard the citizens’ lives and property. This article further discusses the synthesis and various characteristics of the explosives, namely TNT, PETN and RDX. Characteristics of Tri-Nitro Toluene (TNT) Tri-nitro-toluene is a chemical compound, which is the most widely used high explosive. It is pale yellow in color and insoluble in water. TNT is used in mixtures with other substances, which are as powerful as TNT. It is […]

Class & Individual Characteristics of Firearms

Firearm identification is the process that deals with analyzing the bullets and the cartridge cases that are left behind at the scene of the crime to determine if they came from a particular firearm. Class and Individual Characteristics of Firearm decides if the bullet is fired from a suspected firearm. The basis of firearm identification follows the principle of Locard’s principle of exchange. Firearm The surfaces of the firearm that come in contact with the softer cartridge case and bullet contain few marks common to a group of firearms and certain unique marks that make it different from the other firearms- even those of the same model. Thus, class characteristics are characteristics that remain constant to a group of classes, while the individual characteristics are unique to a particular object. Class Characteristics of Firearms  There are several general characteristics associated with the firearm that can help lead the investigation. These include […]

Identification & Nature Of Firearm Injury

 Section 44 of the Indian Penal Code denotes injury as, “Any harm caused to any person in body, mind, reputation, or property.” Firearm injury is caused by using weapons like revolvers, pistols, rifles, shotguns, etc. The nature of firearm injuries caused by firearms depends on many factors, including the type of weapon, the velocity of the projectiles, firing range, among others. The firearm injuries vary greatly. Ordinarily, they cause punctured wounds. But sometimes explosive, contusion and incised wound are also caused. Classification of Firearm Injury Firearm injuries are classified into Entry Wound and Exit Wound. Entry Wound of Firearm Injury Their inverted margins often recognize entry wounds. The inversion of the edges at the entrance wounds is caused by the projectile, drawing the skin inside. The majorly noticed wounds include: Temporary cavity– Cavity formed by the bullet as soon as it passes through the tissue. Permanent cavity– Cavity caused by […]

Internal, External, and Terminal Ballistics

BALLISTICS originated from the Greek word “Ballein”, which means ‘to throw’, and from the Roman word “Ballista”, which means ‘a machine to hurl a stone.’ Ballistics is defined as the study of projectiles and the factors affecting them. The science of ballistics has been developed to facilitate the examination of firearms; ammunition matters related to it. Ballistics is divided into three major types that include internal ballistics, external ballistics, and terminal ballistics. Colonel Godard first coined forensic ballistics. He used the systematic study of firearms and ammunition in the commission of the crime for investigation and identification. The three major classifications are discussed below in detail. INTERNAL BALLISTICS Internal ballistics deals with the study of incidents happening within the barrel of a weapon from when the firing pin hits the primer to the time the bullet exits from the barrel. It deals with: The scratch marks produced on the projectile while passing through […]

Classification of Firearms

FIREARM is a device that hurls the projectile with a force that is supplied by the expansion of gases produced from the burning of a propellant. Firearms are classified into two i.e., Primitive and Modern Firearms. PRIMITIVE FIREARMS  Primitive firearms include five types of firearms. HAND CANNON: It was the earliest type of handgun made of wrought iron or bronze. It was fitted into a frame with leather thongs. These were loaded from the muzzle end with powder, wad, and ball. On igniting the priming charge through the touch hole with a hot iron, fire flashed through the touch hole and then into the main powder charge to discharge the weapon. MATCH LOCK: the entire system and working were similar to hand canon. The only difference in this weapon was the “match” (a slow-burning piece of cord) used to ignite the priming charge was held in a curved hook screwed onto the […]

Searching The Scene of Explosion

Use of explosives for malicious intentions of destroying life and property is known for a long time. Ingenious ways of devising bombs and booby traps using explosive mixtures locally available or by pilfering explosives meant for industrial or defense use are not uncommon in our country. Therefore, the explosive residues collected from the crime scene are examined for several causes, mainly to spot the explosive material, the source, and the intention of the explosion. Ideal Method of Searching of Scene of Explosion The first and foremost rule is to take any victim found to the hospital. However, before beginning with collecting the evidence from the crime scene, it is necessary to ensure that no suspected devices are found that are not exploded. Documentation of the Crime Scene For the purpose of documentation, four primary methods are followed, which is  Report and note-taking Photographs Videography Crime scene sketching and mapping. The […]

Post Blast Explosive Residue Collection and Analysis

The investigation of explosions features a long history in forensic science and covers incidents ranging from accidents within the home or workplace to major terrorist attacks. However, establishing the nature of an explosion can be a significant challenge to the forensic investigator as fire often follows an explosion. This causes complications for the investigators as maximum valuable evidence is then destroyed. Explosives may be solid, liquid, or in gaseous form. The most commonly found explosives in the crime scene include the following: Blasting explosive– Cylindrical form wrapped in waterproof papers and stamped with maker’s name Gun powder– Black, brown, or grey color available in cylindrical, grain, or powder form. Guncotton– It has a look of ordinary cotton. Fulminates– White or grey powders, which are extremely dangerous. Picric acid and picrates– Yellow crystalline or powder form. Ammonal – Silvery brown powder. Chlorate or potash– Crystals or white powder. Arsenic sulfide– Yellow […]

Methods for Detection of Hidden Explosive Materials

Detection of hidden explosives is an inspection process that is non-destructive in nature. It is usually done to determine whether the container contains any explosive material. These are commonly deployed in airports, ports, and border control. Various sampling processes are developed for detection of hidden explosives in public areas as they pose a threat to the population’s life. Explosive detection methods are related to different fields such as Physics, chemistry, biology, etc., and the detection methods include measuring explosive vapor pressure, nitrogen elements in explosives, and explosive coloration, etc. This article further talks about the various technical methods such as bio-detection, explosive vapor detection, detection using multi-energy X-rays, direct detection of black powder, and many such methods employed to detect hidden explosives. Detection Methods of Hidden Explosives Various methods used for the purpose of detection of hidden explosives are as follows- 1. Bio-Detection Method This method can provide evidence to […]

Classification of Explosives

Explosives can be defined as a single chemical compound or a mixture of substances. It may be solid-liquid or gaseous, capable of exerting a sudden and intense pressure on its surroundings when it is initiated by heat, friction, or percussion. Explosives are classified into two categories, low explosives and high explosives, respectively. This classification is based on the speed and chemical composition of the explosives. LOW EXPLOSIVES These kinds of explosives are also known as deflagrating explosives. These types of explosives only explode and do not detonate. Few examples of low explosives include gunpowder, nitrocellulose, cordite. These kind of explosives requires heat, flash, or friction for their initiation. Deflagrating explosives produce relatively low pressure. HIGH EXPLOSIVES These explosives are also known as detonating explosives. They produce high pressure upon detonating. High explosives require a detonation wave as an impulse for their initiation. They are used where shattering effects are required. […]

History About Development of Firearms Since 13th Century

Firearms are any weapon that is used to fire a projectile with the help of gunpowder. They are developed day-by-day with modern technologies by different countries to make themselves superior to others making it extremely dangerous for the people as every person has access in one way or another. Illegal firearms have also come a long way making it easy to access without any trace. For a long period of time, human has been fascinated with the idea of launching projectiles. As our history suggests, humans have been using crossbows for centuries and also used to fight wars with them. The development of gunpowder just enhanced the efficient ways of launching a projectile. And thus, Firearms have come a long way as they were established hundreds of years ago by the Chinese in the 1300s and since then no country has looked back. History of Firearms Firearms started developing after […]

Detection of Homemade Bombs in Forensic Investigations

Homemade bombs(HMBs) are a type of unconventional explosive that can be deployed anywhere in a variety of ways and can cause death, injury, and property damage. The homemade bomb consists of a variety of components which include an initiator, switch, main charge, power source, and containers. To increase the number of casualties of the explosion, the bomb makers will include additional materials such as nail, glass, metal fragments. Other materials may also contain other elements such as hazardous materials. The homemade bomb can be detonated by a variety of methods depending on the intended target and the place of deployment.   Homemade Explosives Information Sources All the information and reference for the construction and deployment of Homemade bombs are widely available to the public by different sources. Different methods of explosives attacks and their assembly are described in detail in the Al-Qaida’s and Jihad’s training manuals. Several books and research […]