Midterm examination concepts and review

Criminal Justice

The polygraph remains a controversial tool in criminal investigation ever since 1917, when William M. Marston, an American professor, first invented it. However, for almost a century now, the polygraph continues to be used in many countries as an important tool not only for criminal investigations, but also in intelligence screening, as a 'pre trial stipulation', and in the recruitment process. The polygraph is a tool that analyses certain physiological changes as a person is subject to interrogation. A forensic psychophysiologist then assesses the fluctuations in the data from the polygraph test and uses them for the 'psychophysiological detection of deception'. It is common for a person to experience certain involuntary reactions or what are known as autonomic responses when he or she is subject to stress. By the simultaneous measurement of physiological changes such as 'electrodermal response', 'cardiovascular changes', blood pressure and breathing patterns, a psychophysiologist infers either truth or deception from the statements obtained from the suspected person.

The polygraph is used in many countries in their criminal investigation process. Despite the several successful cases where polygraph has helped solve cases without other leads, it has not found universal acceptance. As a statement from the American Civil Liberties Union says, "Despite claims of 'lie detector' examiners, there is no machine that can detect lies," "The 'lie detector' does not measure truth-telling; it measures changes in blood pressure, breath rate and perspiration rate, but those physiological changes can be triggered by a wide range of emotions." [Kevin Bonsor] the most common argument is that the physiological changes that are induced are not uniquely attributed to the stress of lying, as there are other factors that can also result in such fluctuations. (BCSSE, 2003)

Voice stress analysers, widely touted as an alternative to polygraphs, were first used by the U.S. army in the Vietnam War to identify Vietnamese citizens from the rebels. Today, we have Computer-based voice stress analysers, which can help identify the stress levels in speech during an interrogation. The essential principle behind the CVSA is that stress affects speech, which can be easily identified. Normal speech is made up of two components namely amplitude modulation (AM) and frequency modulation (FM). It has been verified that during stress the FM component diminishes to such an extent that a computer can monitor this change successfully, thus helping in identifying stress due to deception. The measurement of inaudible fluctuations of human voice or what are known as 'micro-tremors' are used to analyse voice patterns for stress. A recent study commissioned by Department of Defence Polygraph Institute (DODPI) showed CVSA to be ineffective as a definitive lie detection tool. Mitchell S. Sommers, an associate professor of psychology at the St. Louis University, and an important member of the study states, "We tested one of the more popular voice-stress lie detection technologies and got dismal results. Voice-stress analysis is fairly effective in identifying certain variations in stress levels in human speech, but high levels of stress do not necessarily correlate with deception,." (Gerry Everding, 2004) the study found that the CVSA tests proved to be inconsistent. As Sommers says, "In our evaluation, voice-stress analysis detected some instances of deception, but its ability to do so was consistently less than chance -- you could have gotten better results by flipping a coin" (Gerry Everding, 2004)

2) Preserving the Integrity of Crime Scene is of utmost importance for the case to be solved swiftly and accurately. Most often the entire case may hang on the careful, methodical and efficient manner in which the crime scene is preserved, the initial data gathered, analysed and presented. That is to say that the professional manner in which the crime scene is handled would make all the difference between justice being served and a culprit escaping punishment. The first and foremost task for the officers who initially respond to the crime scene is to secure the perimeter of the crime scene. It is not uncommon for investigators to arrive at the crime scene that is disturbed by relatives and curious bystanders resulting in the destruction of evidence. Erecting barrier posts and using barrier tapes can help in securing the perimeter of the crime scene. The next step is evidence collection. Processing a crime scene without disturbing the evidences is a difficult task and investigators should take every precaution to gather evidence without affecting the crime scene. (GSA)

Crime scene stepping pads' can be used for walking around the area without damaging potential evidences. Photographs and video must be taken before proceeding with the rough sketching around the crime scene. For this purpose 'crime scene sketch kits' must be used. Evidence should be gathered using appropriate evidence collection tools so as not to erase the fingerprints or cause any other damage. It is important for the investigator to carefully consider and gather even microparticle evidences using micro evidence gathering kit. Evidences gathered should be properly catalogued and stored in 'tamper resistant evidence bags'. Evidence collection envelopes with transparent or viewing capabilities are appropriate as they allow for physical examination of the evidence without having opening the packs. Also, evidence bags pre-printed with identification data offer an easy way to collect, store, record and present information from the crime scene. (GSA)

3) in spite of the rapid advancements such as DNA analysis, fingerprints still continue to be the mainstay method of identification in criminal investigations. Optical, physical and chemical processes are the three main methods of enhancing latent fingerprints. The appropriateness of any one particular method is usually determined by the nature of the crime scene. However, optical processes offer the best non-destructive method of fingerprint analysis. Even in cases of fingerprints processed by chemical and physical methods, optical processes such a colouring; luminescence, etc. enhance the fingerprints significantly. Latent fingerprints are most difficult to process and it is essential for the analyst to have an excellent knowledge of human secretions and environmental effects. Fingerprint powders are used to detect specific chemical compounds. (Aluminium powders, magnetic powders, luminescent powders, etc.) However, successful detection using fingerprint powders requires the presence of at least 500 to 1000ng of the material. Even then powdering continues to be the most common fingerprint identification technique.