This paper assesses whether and how common characteristics of jury members or peer voters affect the outcomes of voting systems. In particular, we analyze to what extent these common features result in voting bias. We take as a case study the Eurovision Song Contest for which an extensive amount of historical data is available. In contrast to earlier studies we analyze the impact of common factors on the bias individually for each country, which is necessary to substantiate the publicly debated accusations of regional block voting by certain groups of countries. We establish strong evidence for voting bias in the song contest on the basis of geography, even after correction for culture, language, religion and ethnicity. However, these effects do generally not correspond to the usual accusations. We believe that our findings extend to all instances where groups of jury members or peer voters share certain common factors, which may cause voting bias. It is important to identify such structures explicitly, as it can help avoiding bias in the first place.