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Increasing population growth, crime rates and new resistance to expansion of community services have all contributed to increased case loads for law enforcement.
The polygraph, when properly used as an investigative tool to eliminate the wrongfully accused and identify the guilty, can provide the investigator with a more efficient and productive use of his case time.
Unfortunately, misunderstanding and misuse as to the polygraph’s role in the investigative process still persist. The following is an attempt to describe the polygraph’s function in criminal investigations, its limitations and some of the basic procedures recommended for an accurate and productive examination.
POLYGRAPH PRINCIPLES AND PROCEDURES
Investigators should be aware that there are two primary applications of the polygraph in criminal investigations; Diagnostic and Interrogatory. Diagnostic applications seek as their ultimate goal, a successful determination of truth or deception.
Interrogatory polygraph is less concerned with the issue of truth and usually seeks a confession of wrongdoing from the suspect. Diagnostic polygraph requires an examiner with considerable training and education using carefully constructed questioning techniques that provide scientific analysis of data while interrogatory techniques essentially use the polygraph instrument or even non-functioning boxes with lights and wires as a prop to induce sufficient fear in the suspect so that his only recourse from emotional anguish is confession. Diagnostic polygraph examinations have been admitted into court as evidence, while interrogations using polygraph as a wedge to confessions frequently have been ruled as inadmissible in court.
A rule that investigators may want to follow is to choose the polygraph examiner as if yourself were going to be requested to submit to take an exam. As many of you have heard, the polygraph is only as good as the examiner.
The polygraph instrument records physical changes related to the autonomic nervous system, the so-called involuntary physiological responses, and not just any change from the normal physical recordings. These are involuntary controlled by various centers in the brain.
The psychological stimuli that activate these involuntary responses are two; The emotion of fear, specifically fear of being detected in a lie and the consequences of being caught in that lie; and conflict between what the untruthful subject knows to be the truth and his physical and verbal attempt to portray the opposite.
The polygraph examiner must be advised with relevant information pertaining to the case facts collected during the investigation. The examiner will generally discuss the issues that will be covered on the examination with the investigator. This is important in order to address the issue that the investigator wishes resolved. The examiner may then massage this information in order to fit the technical limitations and conditions that the proper polygraph technique requires.
At this time, certain procedural issues should be addressed and resolved. These issues would include who is authorized to receive the results? Who will be allowed to view the test? Is the subject in custody and if so who will transport him to the testing facility? How will custody be maintained? Will the reading of Miranda be required? If the subject is a juvenile, who will accompany this minor and sign the necessary release forms? Is the subject represented by counsel? Will counsel be allowed to be in the polygraph suite? Will the polygraph procedure be audio or videotaped?
At the time of the actual test, the subject will be required to read and sign the necessary release forms. These forms state that the subject has agreed to submit to the test and the results of the test can be made available to the requesting agency and any other parties that are involved in this process. If the test is being conducted on behalf of a law enforcement agency, the subject should be read his Miranda Rights and no person should be tested without their consent. Other release forms are generally filed out at this time. These forms will include their permission to audio or videotape the session, forms that deal with their medical information and any other forms that the examiner may need to assess the subject’s overall well being.
The examiner will then conduct a pretest interview with the subject in order to determine the facts and circumstances as they are known to them. This affords the subject the opportunity to explain their side of the story. During this phase, the examiner is also assessing the subject’s overall suitability to be tested. This area would include the subject’s mental, physical and emotional state at the time of the test. In some cases, the examiner may determine that the subject is not suitable for polygraph testing at this particular time. The examiner may reschedule the polygraph for a later date depending on the issues revealed during the pretest.
During this phase, the examiner is also allowing the subject to clarify or expound on any previous statements made. The examiner will generally ask a series of questions that are designed to draw out the subject’s verbal and non-verbal behavior. Information is developed regarding the subject’s overall feelings regarding the issue under investigation. During this phase, the subject will offer explanations or make statements which may later prove to be useful during the resolution phase.