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Fuzzy Logic & Profiling




Fuzzy logic is used by mathematical sciences, it has found little or no application in the social sciences, especially criminology. As a mathematical system, fuzzy logic generalizes the Boolean logic and can be a very useful tool for the social sciences, where concepts and terms involve shades of meanings.

Descriptions of suspects that police officers receive are often fuzzy in nature. They are described as “tall”, “dark”, “young,” or even “rude”, terms that are imprecise and admit a range of possibilities. In fact, policing itself involves many issues that are fuzzy and difficult to measure. For example, officer’s services are often evaluated as being “good” or “average,” while gang activity related areas are described as “dangerous” or “rowdy”. All these characteristics are essentially fuzzy, and difficult to use with common statistical techniques.

In everyday conversation we use imprecise terms like “it’s a hot day”, “it’s an early morning meeting”, and “there is only a short time allotted to each speaker.” Ordinarily, we understand intuitively the implied meanings of these terms even though each is individual-specific. Thus, for some people, early morning implies a time period before 9:30 a.m., while for others it may be 6.00 a.m. Yet we can communicate easily in such fuzzy terms.  Human brain is not a computer. “The difference between human brain and the computers lies in the ability of the former to think and reason in imprecise, nonquantitative terms.” It is this proficiency that makes it possible for humans to decipher different scripts and handwriting, comprehend a variety of sounds, interpret multiple meaning responses, and focus on information that is relevant in order to make decisions.

The unreliability of witnesses in identifying criminal suspects is well known to most police officers. Police detective work is dependent on deciphering patterns determined by habitual actions of offenders. In the commission of almost any kind of crime, every offender adopts a fixed mode of behavior in terms of chosen time period, target preference, region of operation, and even the manner of committing the crime. In police terminology, this behavior is described as the “modus operandi” of the offender, and a good detective attempts to establish this by looking for recognizable patterns in the commission of a crime. Thus, in burglary cases, the pattern sought is the time, place, mode of entry into the premises, and items stolen or left behind. In serial killings, apart from the place, time and mode of killing, characteristics of the victim, nodes of the residence, workplace and acquaintances of the offender may form the set pattern.


For example; a new auto theft offense will be analyzed about its attributes and for its membership values in each parameter. Some definite information will always be available, such as the make of the car and place of theft. Based upon the information provided by the complainant or witness, the investigating officer can then assign the values upon the grade of membership into other parameters.

Each of the fuzzy characteristics that the witnesses provided could thus be reduced to a range of numbers on a suitable scale. These given values, the minimum and maximum values provided by the subjective judgment of each of the witnesses could then be determined. The investigator could use the average of the min-max values or other combinations, like min-min and max-max to experiment with different kinds of profiles. This may be determined by judging how well the information matches with other evidence. 

The understanding that certain variables are fuzzy in nature will enhance police capabilities and can also improve our understanding of police behavior, action, and organizational culture.

The reasons  why police officers stopped and questioned a particular “dark”, “lower class” person may perhaps be explained by knowing that these are fuzzy parameters. The police officers may be using a graded scale to make their decisions in which not every dark, lower class person is a suspect but some particular ones are,  these parameters have a high value.


Acknowledgements:

 The Police Department; 
https://www.politie.nl/mijnbuurt/politiebureaus/05/burgwallen.html and a Chief Inspector – Mr. Erik Akerboom                                 ©



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3.      Techniques of Crime Scene Investigation.2012
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5.       Pathology.2005  
6.      Forensic DNA Technology (Lewis Publishers,New York, 1991).
7.      The Examination and Typing of Bloodstains in the Crime Laboratory (U.S. Department of Justice, Washington, D.C., 1971).
8.      „A Short History of the Polymerase Chain Reaction". PCR Protocols. Methods in Molecular Biology.
9.       Molecular Cloning: A Laboratory Manual (3rd ed.). Cold Spring Harbor,N.Y.: Cold Spring Harbor Laboratory Press.2001
10.  "Antibodies as Thermolabile Switches: High Temperature Triggering for the Polymerase Chain Reaction". Bio/Technology.1994
11.  Forensic Science Handbook, vol. III (Regents/Prentice Hall, Englewood Cliffs, NJ, 1993).
12.  "Thermostable DNA Polymerases for a Wide Spectrum of Applications: Comparison of a Robust Hybrid TopoTaq to other enzymes". In Kieleczawa J. DNA Sequencing II: Optimizing Preparation and Cleanup. Jones and Bartlett. 2006
13.  "Microscale chaotic advection enables robust convective DNA replication.". Analytical Chemistry. 2013
14.  Sourcebook in Forensic Serology, Immunology, and Biochemistry (U.S. Department of Justice, National Institute of Justice, Washington, D.C.,1983).
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