One influential strand of public policy-making theory imputes considerable autonomy to civil servants (and politicians) from social pressures; and, in Heclo's variant, conceives of policy makers as engaging in a benign process of social learning, the results of which benefit society. In this article we use the campaign to enact legislation for voluntary sterilization as an example of such a process. The analysis is based on archival records of the deliberations of the Brock Committee (1932–34), established to investigate the desirability of sterilization; it demonstrates how the committee attempted to develop a stronger case for the measure than warranted by the scientific evidence. We argue that the content of the Brock Committee's deliberations conforms in broad terms to the predictions of social learning theory, but that the process was more complicated than this framework would suggest, involving a significant element of interest-group lobbying, thereby weakening the autonomy of state policy makers. Furthermore, the deliberations themselves give cause to revise the laudatory view, more or less explicit in social learning theory, of policy experts' machinations.