Criminal Investigation--midterm Essays

Midterm Essays

Criminal Investigation Midterm Essays Jake J. Koppenhaver

CJ-210 Professor Brown February 9, 2008

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Midterm Essays Discuss in detail the pros and cons of polygraph examinations in the investigative process. Also, describe the operating principles of a polygraph and discuss why polygraphs are not universally accepted as scientifically valid and reliable. The polygraph test, originally invented in 1917 by William M. Marston and made famous in the case of the missing Lindbergh baby, is a form of psychophysiological detection of deception (PDD) examination. It has gained rapid momentum in the investigative field in the United States in recent decades, and has been the basis of other such technologies. Despite the law enforcement fame this device has, it is only legally recognized in about ten countries; Scotland Yard, arguably the world’s most famous investigative agency, does not employ the polygraph in their cases. Polygraphs measure certain key stress elements in the human body, specifically changes in heart rate and blood pressure, rate of breathing, and level of electrical conductance of the skin (or, it monitors sweat glands for moisture). All of these things are common identifying signs of deception, and the polygraph records these readings so that the investigator may interpret them. The accuracy of the polygraph is extremely high, but much of the debate over this tool does not revolve around its accuracy but the interpretation of its results. While the minds and bodies of human beings generally work in a similar fashion, not all work exactly the same. This is a drawback, and goes against the general public’s perception of the “lie detector” test. It also generates reasonable doubt in most cases, giving results for the investigator and psychologist to evaluate and interpret, two acts that are also different from person to person.

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Describe in detail the steps investigators take in order to ensure the integrity of a crime scene and the procedures used to collect and submit evidence. The integrity of the crime scene is of utmost importance, as it contains the initial—and sometimes the only—evidence of a crime. It is vital for the initial responder(s) to preserve the scene until investigators and crime scene staff arrives. The top priority is to establish a perimeter for the crime scene and contain it. Upon arrival of investigative personnel, identifying evidence is next on the list. Evidence can be found on a person, living or dead, in the general area of the crime, part of the victim or suspect’s belongings, in other rooms of a building they are in, etc. Evidence must be recorded (ways to record evidence are photographs, videotaping, audio recording, and keeping a detailed log of findings). Collection of evidence can be a time consuming process, but is extremely important and can either make or break an entire prosecutor’s case. Along with the previous step, collection must be done carefully to ensure that evidence is not contaminated by any foreign substance. When a piece of evidence is collected, it must be extensively recorded (for example, what it is or appears to be, where it was found, its present condition, any other factors, and who collected it). Accountability is also a large factor in evidence collection and testing; Each time a piece of evidence is examined, the examiner or lab technician must create a separate opening in the item holding the evidence, and reseal it with special tape, initialing it. Evidence is the one scientific method of prosecution that, in itself, does not rely on a human factor in court. It is what it is, and nothing more. The interpretation of the evidence is what can help a prosecutor convict a suspect of a crime, or exonerate a suspect from it. It is vital for the investigative members of a law enforcement agency to be familiar with the statutes and previous findings regarding the evidence of their so as to aid the prosecutor in effectively charging the correct person.

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Discuss the differences between nuclear and mitochondrial DNA in regard to accuracy and ease of acquisition. DNA is a relatively newer form of investigative technology, only being adopted by the Federal Bureau of Investigation in 1989. In this field there are two main components of a cell that are useful in investigations: nuclear DNA (nDNA) and mitochondrial DNA (mtDNA). Nuclear DNA is what most tests are designed to examine, and contains the most genetic material with is from both biological parents of the specimen. Every cell has only one nucleus, therefore finding nuclear DNA is much more difficult. Mitochondrial DNA is a different part of a cell, having to do with the human body’s metabolism, and is much more readily available in a cell, even though its genetic material is much less than the nucleus.

Describe the different processes that are employed in making latent fingerprints visible and how the prints are then examined and compared for possible matches. Fingerprints are perhaps the most widely recognized tool in investigations, popularized by nearly every police and court drama ever to grace entertainment. Fingerprint analysis is an example of nature meeting technology: When the human finger touches a surface it leaves behind a combination of natural oils, sweat, and other substances which the suspect has come in contact with, in the form of the ridges of their skin. These ridges are unique to each person, and are naturally permanent from birth to death. Fingerprints are taken by coating the ridges lightly with printer’s ink and gently rolling them onto paper to display the print for recording purposes. Latent prints can also be recovered through other, recently developed means such as dusting flat surfaces, applying chemicals (iodine, ninhydrin, and silver nitrate), or even various kinds of radiation. Each finger has a different pattern, be it a combination of loops, ridges, and whorls. These patterns can be

Midterm Essays compared to those found in prints at crime scenes and to databases such as AFIS (Automated Fingerprint Identification System) or even other such databases such as missing children registries and immigration records. While complete prints are always preferred to incomplete, partial prints are useful as well. Either manually or in a computerized fashion, investigators can match the identifying patterns from the partial to a complete fingerprint, albeit sometimes at the cost of reasonable doubt.

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References Osterburg, James & Ward, Richard (2004). Criminal Investigation: A Method for Reconstructing the Past. University of Illinois: Anderson Publishing.

Wikipedia (2006). Polygraph. Retrieved June 11, 2006, from web site: http://en.wikipedia.org/wiki/Polygraph#Admissibility_of_polygraphs_in_Court.

Ramsland, Katherine (2005). The Polygraph. Retrieved June 11, 2006, from web site: http://www.crimelibrary.com/forensics/polygraph/index.htm.