The rigorous analysis of socio-technical systems is challenging, because people are inherent parts of the system, together with devices and artefacts. In this paper, we report on the use of PVS as a way of analysing such systems in terms of Distributed Cognition. Distributed Cognition is a conceptual framework that allows us to derive insights about plausible user trajectories in socio-technical systems by exploring what information in the environment provides resources for user action, but its application has traditionally required substantial craft skill. DiCoT adds structure and method to the analysis of socio-technical systems from a Distributed Cognition perspective. In this work, we demonstrate how PVS can be used with DiCoT to conduct a systematic analysis. We illustrate how a relatively simple use of PVS can help a field researcher (i) externalise assumptions and facts, (ii) verify the consistency of the logical argument framed in the descriptions, (iii) help uncover latent situations that may warrant further investigation, and (iv) verify conjectures about potential hazards linked to the observed use of information resources. Evidence is also provided that formal methods and empirical studies are not alternative approaches for studying a socio-technical system, but that they can complement and refine each other. The combined use of PVS and DiCoT is illustrated through a case study concerning a real-world emergency medical dispatch system.