a spatial analysis of random gunfire incidents in dallas, tx

A Spatial Analysis of Random Gunfire Incidents in Dallas, TX.

Chad SmithGeography Undergraduatechad@unt.edu

Objectives of Research

Determine the difference between incidents of random gunfire (RGF) and reports of RGF.

Determine the demographic profile of the RGF incident locations.

Determine the neighborhoods where clusters of RGF occur.

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Definitions

Random Gunfire Incident: – Firing a gun into the air, primarily at night. – Offender does not have intent to harm. – Usually in celebration.

Report: – Call placed to 9-1-1 as a result of RGF.– Does not distinguish between unique incidents

and incidents previously reported.

Dallas Police Department 9-1-1 RFG Calls Received

Assumptions

Reports made within a half mile (2,640 ft.) and fifteen minutes are the same incident of RGF.

The first call received is closest to the incident location.

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Data Sets

Dallas Police Department 9-1-1 RGF calls received from August 1, 2006 to November 31, 2006.

– 4,707 distinct records.– 4,702 records geocoded to a known address.– 5 records were excluded for lack of a valid address.

U.S. Census Data for the 2000 Census.– Block group data– Census Tract data

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Methodology for determining incidents from reports.

9-1-1 RGF records were geocoded with ESRI’s ArcView (9.2) software, using line segment approximation.

Each record was reviewed for concurrent records within the half mile and fifteen minute threshold.

The calls were assigned a value based on the order the RGF call was received.

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Incident

Date Time

1 10/15/2006

1:00 AM

2 10/15/2006

1:00 AM

3 10/15/2006

1:01 AM

4 10/15/2006

1:03 AM

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Sequence of Reports

Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Sequence of Reports

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Results of Classification Process

4,702 reports of RGF were classified as 3,285 incidents.

The typical RGF incident generates 1.43 calls to 9-1-1.

The highest number of reports for a single incident, based on the time/distance threshold, was 31 calls to 9-1-1.

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Reports Made to 9-1-1

Inc

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Distribution of Reports to RGF Incidents

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Demographic Profile Methodology

Census block group data was added to the RGF incidents using ESRI’s ArcView 9.2.

A count of incidents was tallied for each block group and that data was added to the attributes of the block groups.

SPSS, statistical analysis software, was used to define correlations between demographic characteristics and RGF incidents.

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Demographic Profile Results

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Pearson Correlations for RGF

College Graduate -.270

Median Household Income -.180

Without HS Diploma .125

Persons Below Poverty .349

Percent Renter Occupied .133

Gun Crimes & Arrests .437

All correlations are statistically significant to 1% (p=0.01).

Methodology for Spatial Statistics

RGF data was spatially weighted by the number of incidents occurring within the block group.

The Moran’s I model measures the distance between each point and compares that with an expected distance within the threshold (clustering).

The model assigns a Z-score based on standard deviations and an I-score based on similarity between points.

RGF incidents can be ranked by cluster and similarity. Targets: Z-scores >= 1.96 (2 standard deviations).

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Conclusions

RGF can be isolated into specific incidents using a GIS with a time/space threshold.

RGF is correlated with levels of education, median household income, levels of owner-occupied housing and total population.

RGF is significantly clustered in neighborhoods with specific demographic profiles.

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Further Research Needed

Develop algorithm or GIS tool to automatically identify duplicate reports of the initial RGF incident.

Explore the placement of the analysis point for the incident.

Use remote sensing data to validate social disorder near clusters of RGF.

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Further Research Needed

Further Research Needed

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Further Research Needed

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Further Research Needed

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Further Research Needed

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Discussion

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