Crime has gone down by 13 percent in the areas where the city's first 18 crime cameras were installed beginning in 2006, a Temple University professor has found in a study.

With the city in the process of installing 250 cameras following the pilot project, Jerry Ratcliffe, an associate professor of criminal justice at Temple, found the decrease mostly among "disorder offenses" as opposed to violent crime. Ratcliffe and fellow researcher Travis Taniguchi took into effect the spread of crime to surrounding streets.

The first cameras were put up at 12 sites, but some were so close that Ratcliffe consolidated the study to 8 distinct sites.

The results differed widely from the eight locations studied, and some areas showed no impact at all by the cameras. "That crime did not reduce in the surveillance areas of half of the sites examined cannot be ignored," says the study, which calls for further research to understand the different results for each camera. The report is available here. Ratcliffe is a former policeman and author of the new book, Intelligence-led Policing.

Last August The Inquirer did its own analysis of the city's 18 closed circuit crime cameras, which had been installed a year previously. Crime statistics around the cameras showed two trends: Around highly visible, unmonitored cameras, crime went down; around less visible, constantly monitored cameras, crime went up. Experts suggested that the more visible cameras discouraged crime, while the less-visible, fully monitored cameras may have led to more reported crime because police caught more crime as it was happening.

Ratcliffe said some area may not have shown a positive impact on crime stats for this reason. He has submitted his study to the city, which is spending $8.9 million this year to install the new cameras, all of which will be fully monitored and highly visible, combining the best aspects of the two different cameras used in the pilot program.