Over its thirty-four years in Ontario, the Sexual Assault Evidence Kit (SAEK) has gained credibility as the objective technoscientific witness of sexual assault. This dissertation traces the Ontario Sexual Assault Evidence Kit (SAEK) and how it gained stability through ongoing anti-rape activism, technoscientific and legal controversy, and shifting medicolegal practice. It draws on 62 interviews with medicolegal professionals and rape crisis centre workers in Ontario, archival data, media articles, and medicolegal texts to examine how the SAEK was (re )assembled in meaning and in material form alongside new technologies, medicolegal practices, spaces, actors, and expertise. The dissertation's theoretical/methodological approach is guided by Donna Haraway's diffraction metaphor and tools from Actor-Network Theory. The study diffracts the SAEK to examine it as a historicized actor involved in medicolegal practice within shifting heterogeneous networks of medical and legal professionals, anti-rape activists, survivors/victims, and texts, tools, and technologies. This dissertation argues that the design, credibility, and continued use of the contemporary SAEK as a technoscientific witness has been fuelled by legal histories and practices based on distrusting women who report sexual assault. Several key questions are examined in detail: how did the contemporary SAEK gain stability as the technoscientific witness of sexual assault, how were the SAEK and its medicolegal network assembled and reassembled, for what purposes, and for whose benefit? By untangling the histories of the SAEK, this study charts the historical and contemporary controversies amongst scientists, nurses, doctors, lawyers, and feminist rape crisis centre workers about who should use the SAEK, where and how they should use it, with what tools and technologies, and for what and whose purpose. Through this history, the dissertation finds that the contemporary SAEK's stability benefits many medicolegal actors but few survivors/victims. By offering a historicized account of the SAEK, this study contributes to existing literature on the SAEK, anti-rape activism in Ontario, and forensic and medical technologies. The dissertation diffracts the SAEK to contribute to future feminist efforts to imagine more ethical and responsible ways of assembling medicolegal technologies and practices around sexual assault.