Blood transfusions are overwhelmingly safe, with about 0.5 to 3 percent of all transfusions resulting in adverse consequences [6] . A proportion of these adverse events result from error in preparation and administration. Other adverse events are classified as infectious (e. g. HIV/AIDS, hepatitis, human T-Cell lymphotropic virus (HTLV), West Nile virus) or non-infectious (these are commoner and include acute haemolytic reaction, transfusion associated acute lung injury, allergic reactions, graft-host disease). While severe non-infectious complications are rare, case fatality is high. Infectious disease risks associated with blood transfusion in Canada are currently estimated at 1 per 7.8 million units transfused for HIV, 1 per 2.3 million for hepatitis C, and 1 per 153,000 for hepatitis B [7] . For manufactured plasma-derived products, the risk is estimated at less than 1 in 10 million or theoretical [8] . Bacterial infection from contaminated blood products is also possible but routine bacterial screening of high risk products (platelets) and changes in blood collection techniques have reduced this risk significantly. Methods to inactivate pathogens in blood products (those currently known and future threats), have been developed for plasma and platelets and methods applicable to red cells are under development. Canadian blood suppliers are currently exploring the feasibility of implementing these new technologies once they are available [9] . So despite public concern (see Lee [10] ), experts would surely see risk as minimal and theoretical. And they do. But this does not prevent every 'unsafe' blood incident from being rigorously pursued. But this assumes that all experts may have the same goals or different pathways to similar goals which may shape the treatment of the hazard differently. In part they do -the safety of the product and public health. But do different groups of experts have other goals or interpretations which may shape the treatment of hazard in specific ways? This is the broad question explored in this paper, the major contribution of which is to examine the divergence of expert opinion even where science is consistent and the goal universal.