This essay uncovers the curious inclusion of the phrase “casual and involuntary expressions” in the first legal treatise arguing for a right to privacy. Louis Brandeis and Samuel Warren’s 1890 Harvard Law Review article used these unpredictable and almost-undetectable movements to reinforce the need for a new right to be called “privacy” and to distinguish privacy from extant legal protections in response to the pressures of a new media environment. If the point-and-shoot camera could “take” expressions a person did not know she was making, it called into question the extent to which those expressions were ever really her own, and if they were, it instantiated a new sense of what expressing might mean. My reading first shows that the article transformed the question of whether photographs captured, shaped, or created expressions on faces into a legal question by equating one’s involuntary expressions with “personal expressions” covered by copyright. This essay reorients our sense of what privacy protects and what a privacy right might still mean in our contemporary moment, by arguing that instantaneous photography structured both the right to privacy and a sense of modern personality through foregrounding one’s involuntary expressions.