This chapter examines how the balance between effective investigative techniques and the protection of individual rights can, when exploited, lead to wrongful convictions. We highlight the ethical and legal complexities surrounding covert methods, the use of informants, and credibility assessment tools deemed “junk science” such as SCAN and polygraphs. The chapter exposes the significant risk of wrongful convictions associated with unreliable informant evidence, particularly from incentivised testimony. The controversial ‘Mr Big’ scenario technique has raised significant concerns surrounding its potential for false confessions and the lack of independent oversight, raising concerns about its impact on justice.