Explosive cases
a rapid chemical change without an outside supply of oxygen with the liberation
of large amounts of energy, gases and heat due to exothermic reaction. There is a
difference between an explosion and a detonation.
Detonation - It is an instantaneous decomposition or combustion of molecules
of explosive, accompanied by heat, sound and short
lived light. Ex TNT, Gelatin.
Explosive are classified according to -
1) Rate of reaction -
i) Low explosive Ex gunpowder, nitrocellulose.
ii) High explosive Ex RDX, PETN
2) According to sensitivity -
i) Primary high explosive Ex mercury fulminate, lead azide,
lead styphnate.
ii) Secondary high explosive Ex TNT, RDX, HMX, PETN.
3) According to occurrence -
i) Military explosive
ii) Industrial explosive
iii) Water explosive
iv) Emulsion explosive
v) Explosives
vi) Pyrotechnics
vii) Propellants
viii) Non explosive mixtures
Every crime scene is a rich and important source of
evidence. Explosion crime scene always needs experienced and systematic
approach.
Upon arrival at the scene, first responders (law enforcement
officers, firefighters, or emergency medical services) must evaluate the scene
of crime speedily and carefully to determine the sequence of action to be
taken. The evaluation includes the scope of the incident, requirement of
emergency services, safety as well as evidentiary concern.
He should initiate the rescue of injured or trapped victims.
Wait for the removal of fatalities as it needs authorization.
He should establish a command post/ command system for
contact and line of communication with authorities and with other public safety
personnel).
He should request emergency services from bomb technicians,
firefighters, and law enforcement officers.
Consider and Identify scene hazards, such as structural
collapse, hazardous chemicals, and beware of secondary explosive devices. If any
secondary device is located, immediately vacate the whole area and contact bomb
disposal personnel.
He should preserve the potentially transient physical
evidences i.e. the evidence present on victims and the evidence that may be compromised/contaminated
by weather conditions.
Investigator Role in explosive cases -
The investigator should coordinate with the first responder to assess the current situation and to determine what occurred.
He must clarify that a search for secondary explosive
devices had been conducted. Assess initial scene safety to the extent likely
prior to entry.
Reassess the crime scene requirements (e.g., boundaries,
personnel, equipment).
He must create an entry and exit pathway for personnel.
Traditional evidence such as fingerprint, footprint, tyre
marks, tool marks should also be searched. He should safeguard the preservation
and/or collection of transient evidence.
He must make an attempt to locate the seat(s) of the
explosion(s). Pattern of explosion provide the center point of the explosion
and for this purpose shattered wooden or glass doors, windows, ventilators
should be observed carefully. Effect of flame or hot gases on metallic objects
also provides the location and influence of the explosion on them. Seat of
explosion and the pit formation carry traces of explosive materials and
constituents of devices. Pit dimensions, depth and direction provide intensity
of explosion.
The search pattern in an explosion case should be spiral
method starting from the site of explosion or pit formation.
Huge amount of debris are present at explosion crime scene,
all debris should be handled with patience and perseverance.
He should Identify witnesses, victims, and the presence of
evidence.
In case of live explosive device, main problem is the proper
identification. The investigator should know about the physical appearance of
various explosive materials.
When a live explosive device is present the investigator
should evacuated all the persons and make whole area safe by piling sand bags
around the device.
If bomb disposal squad is not available then submerge the
device in to water carefully up to 72 hours.
Take the photography/videotaping of the crime scene. Take overall
views of the crime scene (e.g., wide angle, aerial, 360-degree) to spatially
relate the items within and to the crime scene and with the surrounding area.This
documentation should be finished preceding to the removal or disturbance of any
items from the crime scene.
He should not rule out the involvement of any vehicle by the
perpetrator.
He must ensure that the chain of custody is started for
evidence that may have been previously collected.
Some questions always in mind of the investigator which
required examination-
Whether the explosion is a malicious intention or an accident?
The material collected from the crime scene is an explosive
substance?
Quantity of explosive substance and its damaging capacity?
Is the explosion by a non-explosive material like LPG etc?
Is any Improvised explosive device is involved?
MR. DEEPAK PAWAR has been working as Finger Print Expert / Police Officer in Finger Print Bureau , Delhi Police at New Delhi since 2001 . He is the senior most Finger Print Expert , attending / visited several scene of crime and solved many crime cases .He has passed M.Sc (Chemistry) and he is the Member of International Association of Identification . He is the Member of Delhi Police welfare association . He is supervising the Forensic , New Delhi District , Mobile Crime Team . He is one of the Expert in the Special Investigation Team held for investigation of important cases . He has been giving fingerprint proficient training to Delhi Police personnel's . He has been Presented / giving lectures on topics related to forensic science . He is also making examination paper of Finger Print proficient course . He is awarded with Police Medal by MHA and Delhi Police.