The factorial survey is a quasi-experimental method for collecting data on human judgements. It builds on the use of vignettes (i.e. fictive descriptions), in which a number of variables or dimensions are simultaneously varied in order to be able to assess their relative importance for the respondents’ judgements. This case provides an account of how we used the factorial survey in a mixed methods research project, whose aim was to model social workers’, police officers’ and prosecutors’ individual judgements about the seriousness of intimate partner violence. Each respondent in the study (N = 39) judged 100 randomly constructed vignettes portraying situations involving intimate partner violence. The univariate and multivariate statistical analyses based on these data revealed which dimensions influenced a particular respondent’s judgements about the seriousness of the abuse, how much each of these dimensions affected the judgements and in what ways they shaped the judgements. Data generated by means of interviews and focus groups were used to answer questions about why the respondents had weighted the vignette information in the ways indicated by the statistical analyses. This mixed methods approach to collecting data may be used both for studying professional judgements and for developing professional judgements.