Prof. Lee Smithey and Swarthmore students have created a detailed picture of homicides in Delaware County at Swarthmore College. You can find the project website here, and the data visualizations are available here. WHYY did a nice write-up about the project here. It was clearly a lot of work to piece together this data and its been the work of many classes of students.
The data can be filtered by type of violence, gender, age, race and other factors. The trend appears to show a pretty consistent level of violence throughout the period of study, the percent change over the period is dominated by a drop at the end. It does seem that violence at least in Chester City may have dropped in more recent years.
Its clear the most of the violence is clustered in two parts of the county, and that black victims overwhelmingly dominate the numbers. You can add an overlay showing median incomes and its almost a perfect match to where violence is occurring. Many local services, such as policing, are handled in much of the county by municipalities. So the communities that most need services are also those with the fewest resources to offer them.
This is a great dataset to have and I hope it drives many discussions going forward.