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A Numbers Game 

Data proves rising murder rate in Houston cannot be blamed on Katrina evacuees.

Originally published in Investigative Reporters and Editors (IRE) Journal March/April 2007 issue

On one particularly hot Houston evening last summer, a crowd of frustrated citizens flowed into the halls and aisles of Grace Presbyterian Church. They sensed a growing problem on the streets of Houston and wanted answers from the city's mayor and police chief.

"Failure is not an option," one citizen told the mayor.

The demands came nearly one year after Hurricane Katrina sent 150,000 evacuees to settle in Houston, and police admitted the homicide rate in the city had increased dramatically. The official word from the public relations staff at the Houston Police Department: Blame the evacuees from New Orleans for the murder rate increase.

As Houston Police Capt. Dwayne Ready told The Washington Times last October, "We recognize that the homicide rate is up as far as raw numbers and as well as percentages relative to the population. We also recognize that Katrina evacuees continue to have an impact on the murder rate."

Curiously, the police department remained focused on telling the public about the recent rise in homicides, but when pressed by an increasingly disgruntled public about other crimes, the department would sometimes cite statistics showing an overall decrease in violent crime. Police sidestepped talking publicly about other violent crime trends or other neighborhoods. They said they had only studied "the Katrina effect" as it related to homicides.

Houston TV station KHOU executive producer David Raziq, producer Chris Henao, photojournalist Keith Tomshe and I wanted to know why. So, we decided to begin our own independent investigation of crime trends throughout the city. Our analysis eventually would cast doubt on claims that Houston's growing problem with violent crime could be blamed solely on the evacuees. In fact, we saw strong evidence to the contrary.

We began by requesting the most detailed incident-level data available in Houston for every crime committed in the city throughout the last three years. Each crime record we received contained information on the offense date, an incident number, offense code, police beat, census tract, city, county, time of offense, day of week, premise code and the address of the crime. We received the information on nearly 450,000 crimes in a plain-text file, which we imported into Microsoft Access.

To search for trends, we honed in on the offense code assigned to each incident. The offense code is a numerical description of a specific kind of recorded crime. We had to use the police department's data dictionary to decipher what each code really referred to because the records track several hundred different kinds of crime.

The offense code would provide details critical to our analysis. The Houston Police Department had told the public the number of serious assaults was down across the city. It was a true statement -- but only if you lumped all kinds of those assaults together.

Examining the more detailed offense codes revealed the larger story because it showed the total number of "assaults" that were really shootings or stabbings compared to those that were much less serious. It turned out that the number of less serious assaults were down. But, we discovered a dramatic increase in the worst of the worst: aggravated assaults with deadly weapons.

We continued our research by transferring our findings to Microsoft Excel spreadsheets to look for changes over time in the number of incidents for each offense code. Looking at the rate of change, our calculations showed that the number of aggravated assaults with deadly weapons in Houston had actually gone up by 22 percent in just two years' time.

For example, during the first seven months of 2004, Houston saw 1,804 incidents of aggravated assault with a deadly weapon -- the kind of assault that is so serious one expert called each incident "a failed attempt at murder." By 2005, that number jumped by 9 percent to 1,976 incidents. The surge accelerated to 2,209 in 2006.

Digging deeper, we uncovered more disturbing trends in other crimes. Home burglaries by forcible entry were up more than 25 percent over the last two years. Robberies of gas stations were up 73 percent in one year and the surge in this crime also began a full year before Katrina.

We also wanted to know how these crime surges were changing our neighbors, block by block. In order to look for hot spots, we used ArcView GIS mapping software to show the location of all 6,000 incidents of aggravated assault with a deadly weapon.

We used police beat and census tract information to help verify the accuracy of our map. We decided to plot each year's incidents separately so we could look for neighborhood shifts in this crime over multiple years.

Once we had our maps together, we asked Dr. Ned Levine, the author of a program called CrimeStat, to work with us as we continued to narrow in on hot spots.

CrimeStat is a special statistics computer program funded by grants from the National Institute of Justice and used by police agencies across the nation to discover crime trends. It allowed us to see statistically significant relationships among clusters of incidents, going beyond what our other programs could reveal.

For instance, looking at a spreadsheet alone, we never would be able to see relationships among incidents that might be 15 feet away from each other but in different zip codes. CrimeStat has a number of different ways to search for hot spots. We chose a function called "nearest neighbor," which allows you to spot areas that have a certain number of incidents within a set distance from each other.

The research collaboration uncovered a number of new hot spots that had sprouted up all over Houston, and it showed shifts in where clusters of crime were occurring. It was information we knew residents in those neighborhoods -- not to mention the police force -- would need to know.

However, before rushing to air the story, we wanted to make sure we were right. We asked two criminologists at the University of Houston Downtown and a third expert in crime analysis to check our work. All three researchers confirmed we had run the numbers correctly. What's more, they confirmed the crime surges we discovered were "significant events" that obviously had begun before Hurricane Katrina struck. They concluded that some of the more serious forms of violent crime were indeed on the rise in Houston.

Finally, we took our findings to the Houston Police Department. We presented our analysis to the department's top public information officer, who shared our numbers with the department's crime analysis division.

"They don't have any heartburn over it," Capt. Dwayne Ready said. "So, I would agree it is probably a fair reflection."

The police remained steadfast in telling us that violent crime rates were down if you used overall numbers and considered population. Ready told us he thought his department already knew about all of the hot spots we discovered. He did not provide any documentation when we asked.

With that said, we were finally ready to reveal the city's new hot spots for violent crime. If Houston police knew about them, they certainly had not told the public. Whether or not they attribute the action to the KHOU story, the city of Houston recently announced a new task force intended to curb the rising trend in robberies of gas stations throughout Houston.

We knew we would never have enough on-air time to tell our viewers about crime trends in every neighborhood throughout the fourth-largest city in America. We went to our Internet staff and asked them to help us create an interactive map that people could use to zoom in on their own neighborhoods. Our Web staff created a simple but valuable way for our viewers to zoom in to see crime incidents along the very streets they live on.

Almost immediately, we found out just how hungry our viewers were for local information like this. Our Web traffic for these searchable maps outpaced the number of hits a standard news story receives by more than 1,000 percent. Viewer after viewer wrote in to thank us for helping them to learn more about their own areas. We gave our viewers the tools and information they would need to make up their own minds about crime trends in their own neighborhood.

Mark Greenblatt is an investigative reporter for KHOU-Houston. His work has been recognized with five Edward R. Murrow Awards and an IRE Award, among other honors.

click to enlarge Houston officials blame a rising crime rate on Hurricane - Katrina evacuees, but a media investigation shows the city's - homicide rate was rising even before the storm sent - 150,000 evacuees in the city.
  • Houston officials blame a rising crime rate on Hurricane Katrina evacuees, but a media investigation shows the city's homicide rate was rising even before the storm sent 150,000 evacuees in the city.


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