In 2010 the European Social Survey included a module on public trust in national police and criminal courts. The included questions were especially susceptible to item nonresponse. This study examines the interviewer and country variability in responding “I don’t know” to these questions using a beta-binomial logistic mixed model, controlling for demographic background variables. The results show that there are large differences between interviewers and countries which are not due to underlying demographic differences between the respondents. The difference in data quality between interviewers and countries make (inter)national comparisons more difficult. More importantly, we could assume that these missing values …