The technique of fire investigation is a forensic domain in which expertise and analogies play a central role. To learn how fire investigators use these analogies to support their work, we conducted an ethnographic study in a Swiss forensic police department. To propose a suitable knowledge-management strategy, we also evaluated the knowledge conservation and sharing within the department. Our results highlighted that actionable knowledge is registered mainly in the investigators’ memories of a few, very experienced, individuals. Without experience with fire-incident investigations, an agent generally requires help from a more experienced colleague, who will then use his memory to find a similar case, which can contribute to the solution of the ongoing one. The research also established that knowledge is exchanged orally during on-site investigations and that knowledge receivers are generally those who are present on the scene. Using these findings, we suggest building a case library to support the externalisation and sharing of knowledge.