With the number of older adult arrestees and prisoners increasing rapidly, legal professionals increasingly provide front-line identification and response to age-related health conditions (including cognitive and physical impairments) that may affect legal outcomes, such as the ability to participate in one's defense or stay safe in jail. The goals of this study were to assess the ability of legal professionals to recognize and respond to age-related conditions that could affect legal outcomes and to identify recommendations to address important knowledge gaps. This was a mixed quantitative-qualitative study. Legal professionals (N = 72) in the criminal justice system were surveyed to describe their demographic characteristics, expertise, and prior aging-related training and to inform the qualitative interview guide. Those surveyed included attorneys (district attorneys (25%), public defenders and legal advocates (58%)), judges (6%), and court-affiliated social workers (11%). In-depth qualitative interviews were then conducted with a subset of 10 legal professionals who worked with older adults at least weekly. Results from the surveys and interviews revealed knowledge deficits in four important areas: age-related health, identification of cognitive impairment, assessment of safety risk, and optimization of services upon release from jail. Four recommendations to close these gaps emerged: educate legal professionals about age-related health, train professionals to identify cognitive and sensory impairment, develop checklists to identify those at risk of poor health or safety, and improve knowledge of and access to transitional services for older adults. These findings suggest that geriatrics knowledge gaps of legal professionals exist that may contribute to adverse medical or legal outcomes for older adults involved in the criminal justice system and that partnerships between healthcare and legal professionals are needed to address these challenges.