The UN describes disorientation or distraction devices as bomb-like instruments designed to daze or warn groups or individuals through some combination of noise, light, overpressure or fragmentation. Common names for handheld weapons of this class include stun grenades, flash-bang grenades, blast balls, sting ball grenades, stinger grenades, lasers and concussion grenades.
Use of stun grenades in crowd control has increased significantly over the past several years, and now these weapons are manufactured by dozens of companies worldwide. They are frequently used alongside other weapons such as chemical irritants and/or kinetic impact projectiles.
Defective and misfiring stun grenades have been identified in several settings where there were limited regulations, quality control processes, or guidelines on their use.
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1960s
Flash-bang explosive devices were initially developed by the British Special Air Service in the 1960s …
… and have been used for military combat training for decades.
1970s
The first documented use of these devices outside training was at Entebbe, Uganda, in 1976 …
… when the Israeli army used them in efforts to rescue hostages.
1977 & 1980
They were used in 1977 in Mogadishu, Somalia …
… and at the siege of the Iranian embassy in London, UK, in 1980.
Today
Transition from military operations to police use occurred slowly over time. Use in urban settings and on civilian populations altered how the weapons were deployed, as well as the resulting injuries.
Specialized law enforcement forces like special weapons and tactics (SWAT) teams initially developed similar weapons to use in hostage situations.
Mechanism of action
Flash-bang or stun grenades are usually constructed like conventional grenades, with an explosive powder that ignites when struck by a fuse. These devices typically generate noise and a bright flash through the rapid oxidation of a pyrophoric metal, such as magnesium or aluminium; this process can generate temperatures in excess of 3,000 degrees Celsius, and the grenades are at least 10 times louder than most gunshots.
When a distraction device detonates, the case ruptures with significant force, so individuals standing near an explosion may suffer traumatic injury from overpressure. The case can also rupture in such a way that high-velocity metal or plastic fragments are sent in multiple directions. These fragments are often uneven in size, shape and direction, and can pose a generalized hazard to anyone nearby.
In addition to the shrapnel risk posed by fragmentation of the device casing, some devices are designed to deliberately scatter high-velocity rubber or plastic projectiles around the blast radius. Finally, projectiles with disorienting characteristics can be fired directly at individuals, carrying with them risks similar to those of KIPs.
When a distraction device detonates, the case ruptures with significant force, so individuals standing near an explosion may suffer traumatic injury from overpressure.
Health effects
Stun grenades are – as explosive devices – by nature indiscriminate. When they are used either as distraction devices to facilitate entry or as a means of crowd dispersal, the limited control users have over their placement may expose unintended targets to the risk of serious injury. When used indoors or in dense crowds, these risks are amplified, and stun grenades can also create hazards through fires, as well as the psychological panic they may provoke.
As with all explosives, stun grenades carry the risk of blast injury. These injuries are complex and result from the pressure waves created by the blast. Blast injuries from nearby explosions can lead to internal haemorrhage, eardrum rupture, lung injury, amputation, fractures and degloving injuries (extensive skin removal that exposes underlying tissue).
In addition to injuries caused directly by the primary blast wave, such as eardrum rupture or lung injury, secondary and tertiary injuries can also occur as a result of these explosive devices.
All weapons are made of both metal and plastic parts that may fragment during the explosion and act as shrapnel. Some weapons, such as sting ball grenades, are specifically designed with fragmentation in mind, to purposefully eject shrapnel across the blast area. Serious injuries have been documented from these unaimed impact projectiles, such as penetrating injuries, skull fracture, severe ocular trauma and enucleation.
Stun grenades burn extremely hot and can cause life-threatening thermal injuries. Furthermore, they can cause fires in structures; these fires have been fatal. Apart from the risks associated with the blast, some distraction devices are designed to be fired from grenade launchers or similar weapons. When aimed (inappropriately) at individuals the blast risk is compounded by the kinetic risk of what is essentially an improvised KIP. Concerns about direct-fire injuries have also been raised following numerous accounts from Colombia of the VENOM system being used in a direct-fire capacity with stun grenades.
Case studies
What has changed?
Since 2016 there has been growing recognition by human rights groups of the hazard posed by the fragmented parts of distraction devices.
Upon detonation, distraction devices may – unintentionally or by design – disperse dozens of metal or plastic shards as shrapnel in a spherical radius without any control over what is hit. These weapons are therefore fundamentally indiscriminate impact weapons when used in the context of crowd control.
A worrisome tendency in weapons research and development is the appearance of varieties of “area-effect” stun grenades and delivery systems, designed to project multiple bomblets at extreme distances, such as the VENOM multiple-launch system used in Colombia.
Blast balls are a type of hybrid stun grenade combining bright lights and loud sounds with chemical irritants.
This hybrid weaponry poses specific health risks: chemical burns and traumatic injuries combined with explosive injuries can be painful, debilitating and challenging to treat from a medical perspective.
