The document summarizes research on policing in the United States. It discusses: 1. Factors that affect police hiring standards and performance such as funding, education levels, age, and racial demographics of officers and communities. 2. Research showing higher rates of force complaints and shootings against minority groups, but also evidence of implicit bias causing officers to be less likely to shoot unarmed black suspects. 3. Training programs that aim to reduce injuries, use of force, and complaints by improving officers' decision making abilities, especially in high-stress situations.