Contemporary public health literature contains an increasing emphasis on the commercial determinants of health including the influence of unhealthy food, beverage and tobacco industries on government harm prevention policy agendas and global sustainable development goals. Effective capture by the industries of the crucial legislative process associated with the harm prevention initiatives would have a detrimental impact on public health. This article proposes a qualitative multi-spectrum prototype legislative capture test with broad application to a range of industries and jurisdictions at all levels of government where legislative capture may be suspected. It is predicated on a finding of significant encroachment of the public interest (PI) by special interest groups and reciprocating beneficial conduct between the lawmakers and the group. The test is populated from a critical case study of key New South Wales (NSW) alcohol industry statutory amendments within a doctrinal and social inquiry/power framework. It relies upon parliamentary records and secondary data to analyse critically the 2015 "fit for purpose" (FFP) reforms to NSW alcohol supply laws and their consistency with the PI and other constitutional safeguards. It aligns the reforms with other research relating to the magnitude of alcohol and gambling industry political donations and the operation of the alcohol outlet post reform approval process. The application of the test to the case study finds that the 2015 FFP amendments are indicative of legislative capture and associated clientele corruption - critical new considerations in the commercial determination of health. It also identifies the commodification of the PI.