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Southwest Oak Cliff Rapist Don’t Overlook the Obvious Sgt. Mark Stallo Dallas Police Department Planning & Crime Analysis UnitDallas, TX.
During the first half of 1996, the City of Dallas experienced several serial sexual assault attacks. One of these series of attacks was occurring in one particular neighborhood, at night and in apartment complexes. Each attack was becoming increasingly more violent. The Sexual Assault Unit Lieutenant, David Goelden, felt that the individual committing these offenses was a recent release from the prison system. He contacted the Computer/Crime Analysis Unit for help. Using Arcview, the Crime Analysts in the Unit were able to help the Sexual Assaults investigators identify the perpetrator and make an arrest. These offenses were geocoded, that is they were assigned to a spatial location on a map (see Exhibit 1), and the locations plotted on a computer generated map.
Fortunately, the Dallas Police Department receives information from the Texas Department of Corrections (TDC) on paroles and releases to Dallas and Collin Counties each month. This data is added to a database each month so that historic information is retained. The information contains descriptions of the individuals paroled/discharged, what they had been charged with, how long their sentence was, when they were actually released and the address where they would be living. (See example of data in Exhibit 2). Exhibit 2
With this release information and knowing that these
particular offenses had only begun occurring in January 1996, in this
particular area of town, the decision was made to make a simple query into the
TDC release database. We were looking
for a black male, under 30 who had been released prior to 1-6-96. Reviewing the data we found that there were
a number of parolees/releasees who lived in the neighborhood where the sexual
assaults were occurring. The first
assumption was that the parolee/releasee had been discharged from prison prior
to January 5, 1998, and would be tagged as a sex offender. After examining the data for parolees who
fit the description and were released from prison for some type of sex crime,
we found that none of the possibilities met the description of the suspect we
were looking for. The next step was to
map all parolees/releasees who broadly fit the description and had been
released between November of 1995 and the beginning of 1996, to find their
spatial relationship to the offenses (see Exhibit #3). The Crime Analysis Team geocoded
the parolee/releasee addresses that the Corrections Exhibit 3
Department had provided. This information was plotted on a map as well. Meanwhile, a list of several hundred parolees that
met the basic description of the suspect was prepared on a spreadsheet and
provided to Lieutenant Goelden, who was in charge of the investigation. The lieutenant looked at the first page and
immediately recognized that one of the individuals lived in the same apartment
complex where an offense had occurred.
With this information in hand, the Lieutenant conducted a further
investigation, while the Crime Analysis Team continued investigating the other
ex-convicts who lived in the area. The person who lived in this apartment complex had been sent to prison for credit card abuse. It has been a general assumption that non-violent offenders do not commit violent crimes. Therefore, this type of person would not have ordinarily been a prime suspect based on the nature of his conviction. Lieutenant Goelden and his detectives checked into
the history of this parolee who lived in the apartment complex and determined
that he had been sent to prison for credit card abuse. They also discovered that the suspect had
taken this card from a sexual assault victim. Knowing that this suspect had committed a similar
crime, the Sexual Assault Unit began investigating the types of transactions
that he had been involved in. They
discovered that the suspect had pawned a couple of articles similar to those
taken from the victims of the assaults being investigated. Specifically, the suspect had taken a ring
and a necklace from one victim. These
items were found in a pawnshop. The detectives were able to charge the suspect with three of the sexual assaults. The suspect was convicted on two counts and was given two life sentences. After his arrest this type of sex assault in this particular neighborhood stopped. Another serial rapist had been sent to prison. The time and space relationship between the parolee and the sexual assaults helped to point the detectives in the right direction in order to solve the crime. This same relationship might have been discovered without generating a map. The point to be made here is to not overlook the obvious. The detectives were able to see a direct relationship by looking at the maps and the tabular data. The potential future possibilities for crime analysts and detectives working together in looking for relationships are quite literally limitless. |
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Crime Analysts' Round Table, Summer 2001
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