Increasing just responses to sexual assault requires understanding how police perceive sexual assault cases and victims, and which legal (e.g., evidence), extralegal (e.g., suspect characteristics), and practical (e.g., convictability) concerns influence their responses in these cases. Using interview data collected in the Los Angeles Sexual Assault Study, we qualitatively analyzed 611 comments made by 52 detectives in response to questions about case processing decisions (e.g., what it takes to arrest) to examine the factors detectives described as relevant to their assessments of allegations as legitimate, victims as credible, and cases as chargeable. Results revealed overlap between rape myths and legal, extralegal, and practical concerns. Specifically, comments referenced rape myths in relation to suspect blameworthiness and dangerousness, evidence, victim cooperation, and prosecutors’ decisions. Comments also revealed some detectives lacked knowledge of relevant legal statutes and case processing guidelines (e.g., unfound criteria). These results suggest that sexual assault case attrition stems from an orientation to prosecutors’ charging criteria rather than probable cause, and organizational factors, such as deprioritization of sex crimes investigations. We recommend that departments adequately staff and equip sex crimes units with investigatory resources and prioritize sex crimes investigations over non-violent crimes. Departments should incentivize sex crimes assignments and screen applicants for quality, experience, and bias. Detectives in these units should undergo regular trainings on unfounding and probable cause criteria and should be required to make arrests when they have probable cause to do so.