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The researchers accessed records from the case management system of the Metropolitan Police, District of Columbia (MPDC), Homicide Division to collect data regarding offenders and victims associated with homicide cases that occurred in Washington, DC, during the 13-year period 1990-2002. While most victims resided in Washington, DC, those who were killed in the city but had resided in the adjacent states of Maryland and Virginia were also included. For each case, addresses of the incident location, the victim's residence, and offender's residence were geocoded using ArcGIS 8.3. ArcView 3.x was used to calculate both Euclidean distance and shortest path distance along the streets between the home addresses of the victim and offender(s) for each case, and then between each home address and the homicide location. The researchers applied the concept of triad as developed by Block et al. (2004) in order to create a unit of analysis for studying the convergence of victims and offenders in space. A triad is the combination of locations associated with each case: the homicide incident, the residence of the victim, and the residence(s) of the offender(s). Multiple triads are formed when multiple offenders are associated with a homicide. For example, three triads would be developed for an incident in which there are three offenders who killed a victim. The researchers believed it was important to include all known offenders because they have different mobility patterns. The researchers categorized the triads according to their geometry. Dots represent homicides where the victim and offender lived in the residence where the homicide occurred. Lines represent homicides that occur in the home of either the victim or offender. Triangles consist of three non-coincident locations; that is, a victim and offender did not live together, and the homicide crime took place somewhere other than either the victim's or the offender's residence. The researchers then classified each triad according to two separate mobility triangle classification schemes: Traditional Mobility, based on shared or disparate social areas, according to Normandeau's (1968) five-category typology. The five categories are Neighborhood Triangle, Offender Mobility Triangle, Victim Mobility Triangle, Offense Mobility Triangle, and Total Mobility Triangle. ; Distance Mobility, based on relative distance categories between locations. The categories are 0.25 miles, 0.50 miles, 0.75 miles, and 1 mile. Normandeau's (1968) five-category typology was then applied to each category. ; Finally, the researchers classified each triad by the neighborhood associated with the location of the homicide incident, the location of the victim's residence, and the location of the offender's residence.