The expression and management of emotions in a police crisis negotiation are often discussed but rarely studied scientifically. Collaboration between university research and police intervention forces (in France and Switzerland) allowed us to transcribe 14 real negotiations. We based our methods on the way Rogan and Hammer (1995) cut out the sequences and calculated an affect score in three real cases of incidents. For a larger sample, we use methods derived from statistical and computer analysis of textual data and automatic content analysis. The first results lead us to renounce using traditional automatic emotional indexing. Indeed, the context of violence and the loss of conversation norms disrupts indexing. We therefore suggest a new context-based indexing. Exploratory statistical analyses then make it possible to visualize the emotional dynamic of the exchanges between perpetrators and negotiators, as well as the evolution of said dynamic in the phases of crisis. First, the negotiator identifies the nature of the emotional expression (structural vs. contextual). In a second phase, the perpetrator expresses negative-approach emotions to which the negotiator responds with positive-avoidance expressions. In a third stage, the perpetrator can evolve towards a negative-avoidance emotion to which the negotiator responds with positive-approach expressions. Finally, the last stage will be that of emotional neutralization initiated by the perpetrator, which allows the negotiator to conquer the lexical space and lead him towards the peaceful resolution of the crisis. The theoretical and methodological consequences of these results are described, as well as the implications for the training of professionals in crisis negotiation.