Analysing Bengaluru blast, forensically

In a bomb explosion, there always is a pattern of the blast which leads to the perpetrator's module.

It’s another day of the cowardice act of terror. An improvised explosive device blast, obvious from the nature having the intensity of the explosion and causing damage was triggered on Bengaluru’s Church Street. Although it was a low-intensity bomb, the impact was such that  shrapnel killed one and severely injured another.

In any case of bomb explosion, there always is a pattern or signature of the blast which generally leads to the perpetrator’s module, though not necessarily specific ones. This analysis can be made easy if the module has done similar misadventures in the past.

The presence of fringe groups or motivated elements with their newer, improvised devices or copying similar devices used by other modules, can never be ignored. However, the type of charge/explosive used, the fuse, the detonator and the timer device, all contribute to the signature of the explosion.

The type of the container used to fill in the elements may differ though, in each explosion. Each blast can use different containers - cooker, pipes, tiffin carrier, metal box etc. Though developed nations do have sophistication to identify the type of explosive used, in few minutes by the kit method, in India, it may take days in the Forensic Science Laboratory.

In the US, the Timer device analysis centre was set up to study the nature of the timer device to identify/establish the type of module behind the explosion. An able investigating officer talks less and carries no prejudice and his conclusion is always based on scientific evidences with an element of common sense.

The biggest source of information in any explosion is the site of the blast. Hence, utmost care should be taken to stick to the best practices as any tampering or contamination of the evidence is disastrous to the whole investigation.

The analysis of the site of the blast, the number and the nature of victims are also considered vital, as many a times, perpetrators may be one among the injured or the dead.

Hence, it is always a best practice to secure the injured victims while the objects recovered from the injured and the dead are vital pieces of evidence. Even the victim’s statement could turn out to be vital of information to the investigators. The success of the evidence gathered from any isolated blast might carry the foot prints of larger terror groups. 

In post explosions, apart from screening the entry and exits of the city, it is always a best practice to seize all the surveillance units, monitor all the communication from and into the city besides declaring the blast site sterile.

Pre blast measures like educating the public, technical surveillance like mobile, email tracking, an independent CCTV police unit etc are essential as they have the potential to prevent major terror attacks besides strengthening the intelligence network. Issuing advisories like compulsory reporting of buyers/ tenants/ lease/ PG and suspicious person or suspicious activity to the nearest police station/toll free number should be mandatory.

A complete post blast investigation also involves detailed examination of the dead with radiological examination during autopsy. The dead may be one of the perpetrators or may carry lot of information about the perpetrator/s like pieces of shrapnel used, timer used, fuse used, explosive used, position of the victim, direction and intensity of the explosions.

Recovery of materials

In the Church Street blast, the recovery of the cloth material and a newspaper sheet gave a clue about the date and possible place of origin. If the same had been obtained with gloved hands and if it is not contaminated, the DNA evidence and fingerprints of the makers of the bomb can be extracted from this material evidence.

Also, the electronic media should play a more responsible role and its role should be limited to assuring and educating the public, help prevent panic and not to venture either directly or indirectly in assisting the perpetrator or interfere in the investigation process.

Even the investigating team should appoint a spokesperson, preferably the police chief, to brief the media - which may not have clues about the about the investigation, witnesses, evidences etc - until the completion of the investigation. In the present case, the police have so far shown professionalism. They did well in quickly securing the crime scene unlike the earlier cases.

Other major detrimental factor in the Indian criminal justice system is the slow pace of the judicial process which is discouraging. It sometimes disappoints the investigating officials and may encourage and embolden the perpetrators. Still, despite all these measures, it is hard to stop the terror activity.

(The writer is a forensic medicine expert and Editor-in-Chief, Journal of International Academy of Forensic Science & Pathology)

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