Larry May's and Kenneth Shockley's discussions of punishment for mob‐based harms fall back on the idea of individual mens rea. They recognise that the mens rea element is complicated by the fact that an individual's intentional actions in the context of mob activity have a collective dimension to them, either because they are ‘group‐based’, or because they are enabled or constrained by the collective's ‘normative authority’. However, their accounts of punishment fail to adequately reflect this complication. We claim that this is because they primarily countenance ‘paradigmatic’ forms of punishment. Part 2 of the article argues that a non‐paradigmatic form of punishment – one that is ‘expressive’ insofar as it publicly communicates a denunciation – can better target the complex relations between the individual and collective dimensions of mob‐based harms. In order to better illuminate the target of such punishment, Part 1 of the article clarifies the relation between individual, shared and collective responsibility for mob‐based harms. Responding to several shortcomings in May's and Shockley's work, we examine the emergence of ‘mob mentality’ and argue that mob beliefs, intentions and norms are dynamically ‘expressed’ (i.e. publicly manifested, communicated and shaped) in and through the situated behaviour of individual mob members.