Evaluation and Assessment of Scene of Explosion, Explosives and Explosive Residues


An explosive is a substance, maybe an element, a compound, or mixture, which is capable of exerting pressure on its surroundings on explosion/transformation.

Role of Forensic Science in Explosives Examination

Forensic Science plays a role in explosives. Explosives studied by forensic personnel are mainly related to mass destruction episodes where bombs are used for illicit activities. The explosive residues collected from the crime scene are examined for many causes especially to identify the explosive material, the source, and the intention of the explosion.

Overall Rules for Evidence Collection

• First and Foremost Rule

The first and foremost rule is to take the victims to the hospital. Furthermore, because evidence can be obtained from both living and dead victims, law enforcement will be required to respond to hospital calls.

• To Ensure That No Suspected Devices Are Present

Make sure there are no suspicious devices present that could not have caused destruction, such as unexploded bombs, before collecting evidence.

• Be Aware

Be aware of the blast’s secondary threats, such as unstable structures, damaged utilities, hanging debris, void spaces, and other physical dangers. Secondary devices and attacks should not be neglected, and this type of incident has specifically targeted first responders.

• Use Aerial Photography

The use of aerial photos is often suggested as it helps in an investigation by providing a wider view of the scene. The photos should be sent to the laboratory.

• Use Wire Mesh Screens

Wire mesh screens should be used to sort through the debris of the explosion as it can hurt your hands.

• Do not- Handle potential explosives yourself

Never collect an unexploded device, it may explode and cause loss to many other lives. Do not handle potential explosives yourself. Contact the bomb squad after clearing and securing the area.

• Clear and secure the area

To preserve evidence and regulate who can enter the scene, a barricade will be placed around the location.

• Call the Bomb Squad

Bomb squad members should deactivate the unexploded device. If a live bomb is found at the blast scene then the bomb disposal squad is called upon.

• Bomb Disposal Unit

Bomb disposal unit Personnel should always wear appropriate clothing to protect themselves. A bomb disposal suit is a heavy suit of body armor designed to withstand the pressure exerted by a bomb, as well as any projectiles launched by the explosive. Trained personnel attempting bomb disposal usually wears it.

• Always photograph the item “as found”

Before touching or collecting the evidence, always photograph the item as found first. Always note the item, its location, measure its distance from two or more fixed objects in the room, on your scene diagram.

• Always note the Evidence and its location

It is important to note the nature of the evidence recovered and also the location from where it is recovered.

• Do not restrict the investigation to a limited area of the blast scene

Do not restrict your search to a limited area as explosive evidence may be found at a farther place. During the collection of evidence, latex gloves should be used to protect hands and to avoid possible contamination.

• Search far and wide from Epicentre

Search far-off areas too for possible fragments. On rooftops, under rubble, and even embedded in other objects or victims, fragments can be found. Always use containers that are clean, acceptable, and unused. To collect evidence and correctly mark it, always use clean, acceptable, and unused containers.

• Always label properly

It is very crucial to label the evidence properly. Between collecting different items, always change your gloves and clean your equipment. Maintain the chain of custody at all times.

• The size of the explosive does not matter

Never underestimate the power of an explosive device by its size even small explosive devices can cause death or serious injury.

• Collect soot deposits

Soot deposits from materials burned during the explosion are likely to settle on surfaces that are slightly further away, such as rooftops and stationary cars. The type of soot deposited may be unique to the explosive material. Such Evidence should also be collected.

• Interview the Witness

Any witnesses to the blast should be interviewed. Witness reports are useful for gathering information about the blast, details of the explosion, and anything relevant, such as the sightings of suspicious individuals during the plantation of the bomb.

• Search for explosive device/bomb fragments

Experts can figure out what kind of explosive device was utilized, as well as its structure and trigger mechanism. It can locate the bomb maker, particularly if a series of explosions have occurred over some time.

Particular terrorist organizations may be known for using a specific type of explosive. An examination into recent purchases of particular substances is frequently done. The government regulates explosives very strictly, so if someone buys a specific chemical, they might be prosecuted. However, because bomb-making materials are frequently stolen or smuggled into the country, tracing the components may be more challenging. The figure shows approximately 4,560 dynamite rods, 600 kilograms of explosives, and thousands of detonators recovered during a security check.

Collect everything, which directs towards the clues of the blast. Do not forget that anything can be evidence such as electronic board parts, utensils, or their parts thereof like detonators, tapes, wires, timers, switches, and batteries.

• Explosive Detection Canines (dogs) ‘Sniffer Dogs’

The use of specially trained dogs is very popular. It may be one of the oldest ways of explosive detection. These dogs have been taught to use their keen sense of smell to discover and track down even the smallest quantities of hazardous material. The dogs might also be trained to sniff out explosive odors on people and their clothing.

• Use of Electronic ‘Sniffer Devices’

The electronic sniffer devices are similar to sniffer dogs. Explosives usually emit a distinct odor that the device can detect. The air is drawn through a filter. Plastic explosives are not easily detected by these devices, in those cases, canines can serve well.

• X-Ray Detector

When dealing with questionable things or containers, X-ray techniques are routinely used in the identification of explosive devices. The Dual-energy technique sends two x-ray beams through the item at the same time. One detects organic materials and displays them in red, while the other detects inorganic elements and displays them in blue or green. These color differences allow for the quick and efficient scanning of items.

Collection of Explosive Evidence

A forensic expert is frequently required to attend the bomb site. So understanding some common methods of evidence collection from a blast scene is also necessary.

The following points should always be kept in mind while collecting evidence:-

• Search Post Blast Debris

Always searches post-blast debris for the potential evidence which may assist in the investigation.

• Search Farther from the Site of Explosion

An explosion’s debris may be burnt or scattered across a large region. Pieces of an explosive device may be thrown farther from the site of an explosion, so an extensive search of the surroundings is necessary.

• Sift Through Rubble

It’s best not to sort the debris with your bare hands because it can cause injury. So use Wire mesh screens for the same.

• Collect Electrical Components of the Explosive Device

Collect all the explosives devices such as fuses, battery components, wires, and blasting caps, should be collected.

• Collect Components of IEDs

Because bombs are frequently hidden in various containers, all possible container fragments should be recovered as well.

• Collect Fragments of Pipe Bomb

In the case of Pipebomb, collect fragments of a pipe bomb.

• Collect Clocks

Clocks are often indicative of the time bomb mechanism inside the device, so search and collect clocks.

• Collect Iron Nails and Ball Bearings

Collect iron nails, ball bearings that are often used in an explosive device to cause greater destruction to those who are exposed. The crime scene photograph below shows a nail congealed in blood alongside a zipper and two ball bearings, found after the Boston Marathon bombings.

• Collect Remote Controls

They are often used to trigger the explosive device.

• Collect Cloth Pins

Cloth pins are often used in Improvised explosive devices. It is used to hold the components and maintain management of explosive device.

• Collect Fingerprints

Often fingerprints are found intact on the components of an explosive device, bombshells, and other relevant evidence. Fingerprints can be created using appropriate procedures in such circumstances. It provides a greater chance of connecting the device to an individual.

• Gather Porous Materials or Objects with Cracks and Ridges

Porous materials, as well as objects with fractures and ridges, tend to collect a lot of useful residues. If found, to collect the same.

• Collect Materials from near the Blast Site

Collect objects such as foam, rubber, pipe threads, cardboard, or anything with a rough surface around the blast zone.

• Collect Relevant Extraneous Matter

Gather any relevant extraneous material, such as hair, fiber, dust, paint, and so on.

• Collect Tool Marks, if any

Collect all the tool marks which are present on the crime scene.

• Collect writings from the Explosive Device or its Parts

If any writings are discovered on the device, these should be collected and preserved after photography. This could lead the officer in charge of the investigation to the perpetrator.

• Swabbing

Swabbing is used to collect soot deposits and other evidence in the case of large immobile items such as buildings. The swabs should be wet using methanol, isopropyl alcohol, acetone, or distilled water before collection. Away from the blast site, control samples should be taken. Swabs should be dried and stored in a sealable clean glass or plastic containers.

• X-Ray Suspicious Items

The suspicious devices should be X-rayed for internal arrangements which will reveal clockwork, batteries, percussion caps, switches, and others.

Packing of Explosive Evidence

The investigating officers should follow the under-mentioned steps while packing the Explosive Evidence:-

Water-soluble explosive and volatile residue should be packed in airtight containers such as clean unused metal cans, glass jars, sealable nylon bags.

Some explosive residues are water-soluble and must be kept dry, while others evaporate fast and must be stored in airtight containers as soon as possible, such as clean, unused metal cans, glass jars, or sealable nylon bags.

Never put the jagged remains of a pipe bomb in the bag.

Ziplock bags should not be used to store explosive residues.

Avoid overfilling the containers.

Do not leave containers unpacked, it may cause breakage.

Do not use packing materials like shredded paper or vermiculite to fill the evidence containers.

Flash powder is very sensitive so it should be packed in anti-static plastic bags or paper packages.

Do not pack the bulk flash powder in metal containers or plastic bags.

Before sending, all the containers should be labeled. The type of material, the date of collection, the investigator’s initials, the case name and number, and any other relevant data should all be included on the label.

Transporting the Explosive Evidence to the Lab while forwarding the explosive evidence to the laboratory, always send the evidence along with a forwarding letter with a brief history of the case and details of the evidence and examination required.

► Always submit control samples and evidence in separate packages if at all possible. If the dirt from a blast site is submitted, take a sample of identical soil from a location away from the blast site, and if a part of rubber molding with blast residues is provided, submit a clean region of the molding as well. Controls should be packed in the same manner that the residue samples.

► According to the conditions of the case, the laboratory should be given as much information as possible, including images, diagrams, witness accounts, and officer reports of a blast site.

► Send explosive evidence through a special messenger rather than regular mail.

► Send only representative samples of the explosive and not the whole bulk.

► Separate the initiating device or detonators from the rest of the explosives. Only one or two detonators are required.

► Inform the station-master that the explosives are being carried on the train.

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