All of CPD's directives are publicly available on the 'net. Submitted for your review:

The CPD's Gang Violence Reduction Strategy -
http://directives.chicagopolice.org/....html?ownapi=1

The links analysis used is based on the research and theory of violent crime spreading proposed by Dr Andrew Papachristos -
http://papachristos.org/Publications...orked_crim.pdf

"I created a ““two-degree”” network. The ““1 rst degree”” entailed extracting all known associates with whom avictim had been arrested during this time period. The simple assumption is that if two individuals are arrested together, they are likely to have some ““association”” or friendship. Thus, a tie exists when two (or more) individuals have been arrested together. The ““two-degree”” network emerges by repeating the 1 rst step for all of the associates of those from the 1 rst-degree networks. This two-step process reveals the network structure in Figure 5.7, which began with 119 homicide victims and grew to a total number of 1,638 individuals——less than 2 percent of the total population in these neighborhoods."