Teargas has followed a markedly different trajectory to its chemical weapons (CW) counterparts over the twentieth century. While the Geneva Protocol of 1925 and the 1993 Chemical Weapons Convention prohibited chemical agents as means of warfare, from the early interwar period teargas gained legitimacy as a technology for domestic policing across the world. Moreover, this role in domestic riot control later became a means for some states to justify its use in military operations. This PhD therefore asks: how did teargas, in the case of British policy, become associated with riot control and policing in the twentieth century, yet prohibited as a means of warfare? Drawing from key concepts in STS and related social sciences, I argue that we can take the technical characteristics of ‘teargas’ (its ‘non-lethality’ or low toxicity) as being co-produced with its social role as a crowd control agent. Furthermore, I argue that by doing so we gain insight into how the ‘non-lethal’ status of teargas was situated within a ‘civilising’ governmentality in Britain. This governmentality both legitimated, and was legitimated by, the authority of scientific expertise. The thesis makes this argument by tracing a historical sociology of teargas in Britain and the empire from 1925 to 1965. Using declassified records from the UK National Archives and sources from newspaper archives, it examines three significant moments in Britain’s construction of teargas as a domestic technology. The first addresses the initial transition from military to colonial policing contexts that teargas made in British policy during the interwar period; the second focuses on Britain’s first use of teargas on populations within the UK during civil defence gas tests during WWII; the third traces the widespread use of teargas throughout the empire from WWII until 1965, examining the emergence of CS gas with the conception of riot control later in this period. Ultimately, I contend that CS, the ‘teargas’ of our contemporary moment, emerged from a sociotechnical imaginary of non-lethal chemical control grounded in ‘civilising’ modes of techno-politics
