Abstract
This paper is based on a case study of a long-term public controversy over the construction of a highway bypass (around Plzen, Czech Republic). Two principal variants of the bypass were proposed.
One of them began gradually to appear preferable, increasingly attractive for experts, but remaining only on paper. In the meantime, however, the other variant became more realistic, pushed through mainly by local politicians and actually constructed.
We show how purification of science from politics (and vice versa) played a key role in the development and ending of the case. Initial expertisation of the case switched to its sharp politicization, when people got frustrated from protraction and indecisive evidence of accumulated expertise.
This turned to be fatal for those who consistently staked everything on "pure facts". We conclude by outlining some general consequences of such a development for both democratic decision making and the political relevance of expertise.