5.5 Explosion and Blast Injury Deaths
Key Takeaways
- Blast injuries are classified in five mechanisms: primary from the overpressure wave itself, secondary from propelled fragments, tertiary from displacement of the body or structural collapse, quaternary from burns, inhalation, crush and other associated effects, and quinary from the inflammatory or toxic effects of additives.
- Primary blast injury concentrates at air-fluid interfaces, producing tympanic membrane rupture, blast lung with pulmonary contusion and air embolism risk, and hollow-viscus perforation; secondary fragment injury is the most common cause of death in most terrorist bombings.
- Investigators do not enter an explosion scene until it is declared safe by explosive-ordnance personnel because of secondary devices, structural instability, and utility hazards, and evidence is worthless if it costs a responder.
- Bombing scenes are federal crime scenes in most circumstances, with ATF and FBI jurisdiction, so the office works within a unified command and does not unilaterally control evidence or the scene.
- Every set of remains and every body part receives its own number, its own location record, and its own radiographs, because fragments embedded in tissue are both identification and weapon evidence.
5.5 Explosion and Blast Injury Deaths
The Advanced Skills List lists "investigate bomb-explosion deaths" under Investigating Multiple Fatalities, which tells you how ABMDI expects the topic to be approached: an explosion is rarely a single-decedent problem, and the investigative structure is a mass-fatality structure even when the count is two.
Explosions in medicolegal practice are not only terrorist bombings. Natural gas accumulations in residential basements, propane and fuel-air events, grain and sugar dust explosions in silos and processing plants, boiler ruptures, ammonium nitrate storage fires, clandestine drug-lab and butane hash-oil events, fireworks manufacture, and military ordnance all produce the same physics and the same injury classification.
Blast Physics
A high-order detonation converts solid explosive to gas almost instantaneously, producing a shock front that travels faster than the speed of sound. The pressure history at a point is the Friedlander waveform: an near-instantaneous rise to peak overpressure, an exponential decay through the positive phase, then a negative phase of below-ambient pressure that draws debris back toward the seat of the explosion. The negative phase is why fragments and glass are sometimes found on both sides of a window frame.
Two physical realities drive most of the medicolegal findings:
- Overpressure falls off very rapidly with distance from the seat, roughly with the cube of distance in free air, which is why lethal primary blast injury is confined close to the device while fragment injury extends much further.
- Confinement multiplies lethality. In an enclosed space the wave reflects off walls, floor, and ceiling, so reflected pressure greatly exceeds incident pressure. An identical device kills far more people on a bus or in a basement than in an open plaza, and this is the mechanism behind the disproportionate fatality rate of confined-space bombings.
The Five Blast Injury Mechanisms
| Mechanism | Cause | Characteristic injuries |
|---|---|---|
| Primary | The overpressure wave acting on the body | Tympanic membrane rupture, blast lung, hollow-viscus perforation, globe rupture, traumatic limb amputation at high overpressure |
| Secondary | Fragments propelled by the blast — casing, added shrapnel, and environmental debris | Penetrating and perforating wounds, lacerations, globe penetration; the leading cause of death in most bombings |
| Tertiary | The body displaced by blast wind, or structures collapsing onto it | Blunt force trauma, fractures, crush injury, head injury from impact |
| Quaternary | Everything else caused by the event | Flash and flame burns, inhalation of smoke and toxic products, carbon monoxide and cyanide toxicity, asphyxia, exacerbation of existing disease, crush syndrome |
| Quinary | Additives and post-detonation biological or chemical effects | Hyperinflammatory states, contamination by radiological, chemical, or biological material added to the device |
Primary blast injury concentrates where tissue density changes — the air-fluid interfaces. In descending order of sensitivity: the tympanic membrane, which ruptures at relatively low overpressure and has historically been used as a rough marker of exposure, though a normal eardrum does not exclude significant primary injury; the lung, producing "blast lung" with pulmonary contusion, hemorrhage, and a real risk of arterial air embolism from alveolar-venous disruption; and the hollow viscera, particularly the colon, which may perforate immediately or hours later.
Traumatic amputation by primary blast, usually through the shaft of a long bone rather than a joint, marks proximity to a very high overpressure and, in a fatality population, is associated with a low survival rate.
A specific scene finding: in a suicide bombing, the bomber is frequently identified by severe fragmentation with relative preservation of the head, which is decapitated and thrown clear, and by the pattern of injury indicating the device was carried on the body. Bone and tissue fragments from the bomber can be driven into surviving victims and responders, which is a documented bloodborne-pathogen exposure route and an evidentiary source.
Scene Control: Safety First, Evidence Second
No part of an explosion scene belongs to the medicolegal investigator until it is released.
- Secondary devices are deliberately placed to kill responders and are timed or triggered for the response phase. Nothing is touched, moved, or approached until explosive-ordnance disposal declares the area clear, and personnel avoid obvious secondary-device locations such as vehicles, trash containers, and the natural gathering points for responders.
- Structural instability after a blast is the second killer. Collapse zones, hanging debris, and compromised load paths are assessed by structural specialists and fire command.
- Utilities — gas, electrical, and process chemicals — are secured before entry.
- Radiological, chemical, and biological survey is performed where a device may have been augmented. Detection is a hazmat function; the investigator's role is to ask whether it was done.
- Personal protective equipment includes respiratory protection, eye protection, and cut-resistant gloves, because explosion scenes are fields of glass and metal shards.
Working inside a unified command, the office documents the position of every decedent and every body part relative to the seat of the explosion, because that geometry is later used to reconstruct the device location, the victim's position and orientation, and in a criminal case the identity of the bomber.
Jurisdiction
Bombings are federal crimes in most circumstances. The Bureau of Alcohol, Tobacco, Firearms and Explosives has statutory authority over explosives offenses and maintains national response teams and certified explosives specialists; the FBI has authority over terrorism and maintains bomb technicians and an evidence response capability. In a significant incident, federal, state, and local agencies operate under a unified command, and the medical examiner or coroner participates as the authority over the decedents while the scene itself is controlled by the lead investigative agency.
This is a place where a Board-level investigator must be precise about roles. The office does not surrender jurisdiction over the bodies, but neither does it unilaterally control the scene, set the search grid, or release evidence. Those decisions are made in the unified command, and the office's leverage comes from participating there rather than from asserting authority at the tape.
Documentation and Evidence
Numbering. Every set of remains and every fragmentary body part is assigned its own unique number and its own recorded location, with photographs in place and total-station or GPS coordinates where available. Commingling in an explosion is the rule, and the numbering discipline is what makes later reassociation and DNA identification possible.
Radiographs are mandatory. Full-body radiography of every decedent and every significant body part is performed before examination. Radiographs locate metallic fragments for recovery, identify device components such as ball bearings, nails, screws, and timer and battery fragments, and contribute to identification through dental and skeletal comparison and hardware serial identification.
Fragment recovery. Fragments recovered from tissue are the weapon. Each is documented for its location and orientation in the body, removed without contact with metal instruments where practical, packaged separately in clean containers, and released to the lead agency's evidence process. Clothing is retained intact and air-dried, because embedded fragments, singeing, and pattern damage are recoverable from textiles long after the body has been examined.
Explosive residue. Swabbing for explosive residue on skin, hands, and clothing is performed with clean, dedicated materials, and every sample is accompanied by a substrate and a field blank control. Cross-contamination is the central risk: personnel who have handled the seat of the explosion do not then swab a body without changing gloves and instruments.
Identification. Because fragmentation defeats visual identification, these incidents run on the scientific primaries — fingerprints, dental comparison, DNA, and radiographic and medical-device comparison — through the full disaster victim identification process, with antemortem data collection through a family assistance center.
A pipe bomb detonates in a crowded transit station. Which blast injury mechanism is responsible for the largest share of deaths in a typical bombing of this kind?
Which finding is most characteristic of primary blast injury?
Investigators arrive at a bombing scene where fire crews are still working. What is the correct approach to recovering the decedents?
Why are full-body radiographs performed on every decedent and every significant body part in an explosion fatality?