In the 1980s, the northern spotted owl controversy challenged US forest service practices. We review the ecological statements produced during the dispute and the political and social issues at stake. We identify the mutual influence of science and management in producing an ecological indicator in a judicial context. We identified phases of category production, quantification and variable construction. We were able to characterize when existing indicators and assumptions are preferred to new ones. It is when (1) the management plan took for granted hypotheses and results produced by science and (2) new results challenging past hypotheses were not taken into account. We propose to complement the introduction chapter by proposals of adaptive management.