Effect of urban closed circuit television on assault injury and violence detection.

OBJECTIVE To evaluate the effect of closed circuit television (CCTV) surveillance on levels of assault injury and violence detection. DESIGN Intervention versus control study design. SETTING Five town/cities with CCTV surveillance and five, matched control centres without CCTV surveillance in England. INTERVENTION CCTV installation and surveillance. METHODS Assault related emergency department attendances and violent offences recorded by the police in CCTV and control centres in the four years, 1995-99, two years before and two years after CCTV installation, were compared. RESULTS Assault related emergency department attendances decreased in intervention centres (3% decrease, ratio 0.96; 95% confidence interval (CI) 0.93 to 0.99) and increased in control centres (11% increase, ratio 1.11; 95% CI 1.08 to 1.14). Overall, changes in emergency department assault attendance in CCTV and control centres were significantly different (t test, p<0.05). Police recorded violence increased in CCTV (11% increase, ratio 1.16; 95% CI 1.08 to 1.24) and control centres (5% increase, ratio 1.06; 95% CI 0.99 to 1.13). Overall, changes in police recording in CCTV and control centres were not significantly different (t test, p>0.05). In CCTV centres, decreases in assault related emergency department attendances and increases in police violence detection were not uniform. CONCLUSION CCTV surveillance was associated with increased police detection of violence and reductions in injury or severity of injury. CCTV centre variation deserves further study.