Explosions: Accidental or Deliberate

In another persona, I write science fiction as well as these science fact pieces. Even fiction requires meticulous research. Once, I looked at explosions and how to make bombs. For a month afterward, all the adverts on my social media sites were for fertilizer. The link? Well, explosions, either accidental or deliberate, require explosives, and the basic chemicals for many explosives just happened to be the same as those for fertilizer.

In fact, Improvised Explosive Devices (IEDs), the ones made by terrorists, are often manufactured from fertilizer—the same stuff as you put on your flowers.

However, not all explosions are terrorist activities. A simple cloud of dust can explode in the wrong circumstances

C6H12O6(S) + 6O2(g) -> 6CO2(g) + 6H2O(g)

This formula describes the explosive qualities of powered glucose (QI, 2005). With dust of any kind filling the air, without rigid safety guidelines a simple spark calls down disaster.

By locating the point of origin of the event, forensic science helps differentiate between accidents and explosions caused by deliberate malice.

Scene Examination

As with fires investigation, the most important part of dealing with an emergency is the evacuation of casualties. Therefore, the scene suffers potential contamination before the start of an inspection. But, these are witnesses to what happened. Their testimony will aid the inspector in the determination of accidental or deliberate damage.

Two types of forensic analysis are required for blast interpretation. The first involves combing through the wreckage for pieces of a potential device and residue of the chemicals used. It may surprise you that residue of the explosive material is left after detonation. Even in a reaction vessel, not all the reagents are completely used up, this also happens with an explosion. Evidence suggests that the outer layer of the chemicals fails to react; the larger the bomb the smaller the amount of residue is deposited. These residues deposit on walls or dropped out as the blast shock wave falters at the limit of expansion. Some residues are found on fragments left from the device itself. Mathematical models suggest where residue will deposit. Investigators collect residue and fragments and transport them to a laboratory for testing (Kelleher, 2004).

Blast wave. credit: Mehr News Agency https://commons.wikimedia.org/wiki/File:Damages_after_2020_Beirut_explosions_1.jpg

For the second type of forensic analysis an investigator surveys the damage surrounding the explosion and uses statistics to calculate the point of origin and the size (charge mass) of the incendiary device. The extent of damage to buildings and windows make reliable indicators of the charge mass. Closer to the initial event the damage is  greater. The further the damage spreads, via the blast shock wave, the larger the charge mass. Using the Method of Least Squares, allows the scientist to perform an inverse calculation as to the size of the incendiary device (van der Voort, 2015).

For those interested in mathematics and statistics, the references contain fascinating reading.

Explosive devices

IEDs are the most common method of deliberate explosions. These include Molotov cocktails and pipe bombs (Reno, 2000). The materials used to create IED are available in the form of fertilizer and other easily obtained industrial oxidizing chemicals, generally nitrates, nitrites, perchlorates, or chlorates (Peters, 2014).

Pipe Bomb.
Credit: https://commons.wikimedia.org/wiki/File:Pipe_bomb_01.svg

Testing for explosives

Once collected, samples are transported to the lab. Here, the initial screening takes place. Many tests exist to identify the various types of explosives (Technical, 2018)  but, with limited space, I will discuss two tests for fertilizer-based ones, as that is where I started.

Spot testing identifies if the chemicals are present. They are presumptive tests and require confirmation. These procedures require absolutely clean equipment as false positives occur from the smallest trace of contaminant.

Diphenylamine test for Oxidising Agents

All of the compounds listed above are oxidizing agents, therefore a quick test for any oxidizing agents present uses  0.1% diphenylamine in sulphuric acid. A few drops of the reagent are placed in a ceramic dish, then a few grains of the suspect substance are added. If a blue color develops, then an oxidizing agent is present (Instrument, 2020).

Test for oxidizing substances.
Credit V.Knipe

Greiss Test

Once confirmation that an oxidizing agent is present, then the Griess test, for nitrates and nitrites, is performed to narrow down the field. This requires two reagents, three for the modified test.

Reagent 1 = 0.1M Sodium Hydroxide in Methanol

Reagent 2 = 4% sulphanilamide + 0.1% n,1-naphthalene diamine dihydrochloride in phosphoric acid

Reagent 3 = Devarda’s alloy (aluminum, copper, zinc)

In a ceramic dish, add 1 drop of reagent 1. To this, add 1 drop of reagent 2. Add a few grains of your suspect material. If a reddish-purple color develops, this indicates nitrite. If nothing develops, then add the 3^rd reagent, Devarda’s alloy. If a pink-purple color develops after the addition of the 3^rd reagent, then this indicates nitrate (Instrument, 2020).

Greiss Test
Credit:V.Knipe

These spot tests are presumptive, therefore confirmatory tests must be performed before a definitive answer is given to investigators. Further testing using Mass Spectrophotometry is required (Peters, 2014).

Case Study 1: Madrid Train Bombing

On the 11^th of March 2004, two bombs exploded on a commuter train at El Pozo station in Madrid, Spain. During the rush hour of that morning, 10 backpack bombs were detonated by Islamic extremists using cell phones. 191 people died as a result of the explosions (incident, 2004). Witnesses report that those attempting to escape the station ran into a third bomb on the platform (Finnegan, 2022). Once the wounded had been taken to medical care, Investigators found an additional three bombs that had not detonated. Immediately, conjecture started that Basque Separatists were responsible for the attack. Although not enough time to examine the debris had passed, people insisted that residue of the explosive Titadine, commonly used by the separatists, was present (Finnegan, 2022).

However, police discovered an abandoned van containing detonators and audio tapes proving that the Islamic extremists Al-Qaeda were involved not Basque Separatists. Once tests on the residue were performed, scientists found that the explosive used was Gomo-2-ECO (Finnegan, 2022).

The detonator bag held latent fingerprints (see article on fingerprints here). A digital photograph of the prints was distributed by the Spanish police (Ryan, 2006). The US FBI joined the investigators, insisting that they had a match from the Integrated Automated Fingerprint Identification database (Stacey, 2005). A Muslim-American attorney, recently converted, Brandon Mayfield was detained in the US. His release occurred only when the Spanish police found a match to an Algerian (Ryan, 2006).

Discussion

As mentioned above, witnesses are an important part of any investigation into explosions, but those very same witnesses started incorrect rumors before any forensic analysis was completed. An investigator must know what to take into account and what to disregard to remain impartial. When completed, forensic analysis of residue provided an answer that defeated the rumors and brought the culprits to justice. The only skip in the road, came when an incorrect match was made with fingerprints. I included this case study to show how easy it is to come to an incorrect conclusion.

Case Study 2: Beirut Explosion

On the 4^th of August 2020, a huge blast destroyed the dockside area of the port of Beirut, Lebanon (Beirut, 2020).  Satellite images of the shockwave allowed investigators to classify it as the Sixth-largest non-nuclear blast in the world (Machemer, 2020).  The blast wave killed 218 people. The ammonium nitrate was of a quality that could be used to manufacture explosives, but the army took no steps to mitigate the danger to people living in that area. Some confusion existed among the various officials involved as to who was responsible for rendering safe the chemicals (“They”, 2021).

Beirut Port buildings after the blast.
Credit: Mehr News Agency https://commons.wikimedia.org/wiki/File:Damages_after_2020_Beirut_explosions_1.jpg

What caused the explosion?

A large quantity of fertilizer was stored in the port area. The incident started with a fire in a fireworks factory located near the stored chemicals, which then caused the fertilizer to explode (Depalma, 2021).  The need to evacuate casualties was problematic as the blast caused shockwaves out as far as 10km and damaged 9 local hospitals. The explosion led to another consequence of explosions, which was the release of noxious gases into the air, adding to the victims requiring hospitalization.

Discussion

The middle east is a volatile area of the world. If knowledge of the warehouse contents had not been known then this could easily have been mistaken for a terrorist attack. Any forensic examination would have shown oxidizing agents, as ammonium nitrate fertilizer is a common source for improvised explosive devices. Only low-ranking officials were detained after the investigation, even though many higher-ranking officials were assumed to know about the danger. This case study is more Forensic Accounting than Forensic Science. I chose to include it because if an investigator had relied on the science then it would be easy to make a mistake. An investigator must include all aspects of a case, science, and other items of interest if they wish to make a correct conclusion.

Finally

In conclusion, the role of the investigator is vital for the interpretation of an explosion. They require extensive training and an open and unbiased mind. In both of the case studies, investigators made  incorrect assumptions. Too easily errors creep into understanding, preventing a proper interpretation of whether an explosion was an accident or deliberate malice.

References

Beirut Explosion: What we know so far. (Aug 11 2020). BBC News. https://www.bbc.co.uk/news/world-middle-east-53668493

Depalma, Ralph & Al-Hajj, Samar & Kobeissy, Firas. (2021). POLICY AND PRACTICE REVIEWS Beirut Ammonium Nitrate Blast: Analysis, Review, and Recommendations. Frontiers in Public Health. 9. 10.3389/fpubh.2021.657996.

Finnegan, J. (Jun 19 2022). 11M: Lessons Learned from the Madrid Train Attacks. Transport Security International. https://www.tsi-mag.com/11m-lessons-learned-from-the-madrid-train-attacks/

Incident Summary (03/11/2004) Madrid Bombing, Spain. Global Terrorism Database. University of Maryland. https://www.start.umd.edu/gtd/search/IncidentSummary.aspx?gtdid=200403110003

Instrument and Techniques Manual. (2019-2020) Centre for Forensic Science. Strathclyde University.

Kelleher, JD., (April, 2004) Explosive Residue: Origins and Distribution. Forensic Science Communications, FBI. https://archives.fbi.gov/archives/about-us/lab/forensic-science-communications/fsc/april2002/kelleher.htm

Machemer, T. (Oct 7 2020) Beirut Blast was Among History’s Largest Accidental Explosions. Smithsonian Magazine. https://www.smithsonianmag.com/smart-news/beirut-blast-was-among-historys-largest-accidental-explosions-180976005/

Peters, KL., (2014). Development of Presumptive and Confirmatory Analytical Methods for the Simultaneous Detection of Multiple Improvised Explosives. FIU Digital Commons. Florida International University. https://digitalcommons.fiu.edu/cgi/viewcontent.cgi?article=2787&context=etd

QI Series C episode 9, (Nov 18, 2005) BBC4. https://www.comedy.co.uk/tv/qi/episodes/3/9/

Reno, J., Marcus, D., Leary, ML., and Samuels, JE. (2000) A Guide for Explosion and Bombin Scene Investigation. US Department of Justice. https://www.ojp.gov/pdffiles1/nij/181869.pdf

Ryan, J. (Jan 6 2006) Report: FBI Problems Led to Wrongful Terror Arrest. ABC News. https://abcnews.go.com/WNT/story?id=1479790

Stacey, RB. (Jan 2005). Report on the Erroneous Fingerprint Individualization in the Madrid Bombing Case. US Department of Justice. https://www.ojp.gov/ncjrs/virtual-library/abstracts/report-erroneous-fingerprint-individualization-madrid-train-bombing

Technical Leader. (2018) Spot Tests. ATF. https://www.atf.gov/laboratories/docs/laboratories/atf-ls-e17-spot-tests/download

“They Killed Us From the Inside.” (Aug 3 2021) Human Rights Watch. https://www.hrw.org/report/2021/08/03/they-killed-us-inside/investigation-august-4-beirut-blast

van der Voort, MM., van Weiss, RMM., Brouwer, SD., van der Jagt-Deutekom, MJ., and Verrault, J., (2015) Forensic Analysis of Explosions: Inverse calculation of charge mass. Forensic Science International. (April 18) https://www.msiac.nato.int/sites/default/files/attachments/fsi_van_der_voort_lowres.pdf