This article reflects on the experience of the two authors as 'experts' during consultations on justice and security indicators for the Sustainable Development Goals. The authors examine how the tension between the indeterminacy of the concepts to be measured - justice and security - and the concreteness of indicators shaped the politics of the consultations. Participants used this tension strategically to destabilize notions of time, space and identity on which knowledge production rests. In doing so, they blurred the distinction between academics, advocates and policy makers. They did this to lay claim to some aspects of implementation while distancing themselves from others. The authors then juxtapose this with personal experience of researching South Sudanese citizens, who challenged and deconstructed that distinction. At the same time, experts at the consultations incorporated an image of these citizens as an ethical justification for the discussion. The authors argue that a more complex sociology of knowledge is required to understand how these global knowledge practices work from the global to the local. Such a sociology of knowledge acknowledges fluidity and grapples with how knowledge practices defer and delimit moments of decision; it requires an ethico-political - rather than just a political- critique.