Making sense of new technologies and their associated risks entails lay people in utilizing various modes of reasoning and making use of a range of interpretative resources at hand to interrogate evidence.  Such sense making is accomplished collectively in ways that are sometimes playfully inventive, and which have regard to ideas of accountability and morally acceptability.  In practice, such bricolage-like processes appear to have certain similarities with the work of everyday scientific investigation.  This paper examines these processes of lay practical reasoning by adopting an analytic stance that is concerned with examining the fine detail of what people demonstrably do in accomplishing such work.  It draws on data generated by number of reconvened discussion groups, which formed a component part of the recent public debate in the UK about the possible commercialization of genetically modified crops.