What is a Polygraph?
 

According to the dictionary the polygraph is a measuring device, which makes a permanent recording of various physiological changes taking place within the body of the test subject as a result of certain psychological stimuli. These stimuli are brought about by asking questions, structured and phrased in a specific way, and by maintaining a certain environmental and emotional climate during the examination.

During the pretest interview, the polygraph examiner will explain your legal rights, explain the polygraph instrument and how it works, discuss the issue, develop and review all questions asked on the polygraph test, cover general background information, and will provide instructions for the actual testing phase.
 

It is expected that anyone who takes a polygraph test will be nervous; however nervousness does not normally interfere with the test . Even though a person has high blood pressure, diabetes, etc., their body has a set of normal patterns. When a person decides to lie, however, physiological changes to take place in the body. Blood pressure begins to increase or decrease. Heart rate can increase or decrease. A person's heart can skip a beat. Blood volume begins to change. These are just a few of the types of physical changes that can occur.
 

What Does A Typical Polygraph Examination Entail?
 

A professional polygraph examination has three phases: a pretest phase, a data (chart) collection phase, and a post-test phase, which includes test data analysis. A typical polygraph examination will last at least two hours, and sometimes longer.
 

In the pretest phase, required paperwork is completed and the polygraph examiner gets to talk with the examinee about polygraph and the issue being tested.
 

The “chart collection” phase takes place in a quiet room where distractions are held to an absolute minimum. The examiner will attach the sensor components to the person and then ask the previously reviewed questions that are designed to be answered “yes” or “no”. Data is collected by the sensors and instrument and a computerized recording of physiological responses is obtained.

In the Post test phase, the examiner will analyze and score the chart data and render an opinion as to the truthfulness of the person being examined.
 

Polygraph Accuracy and Reliability?
 

The polygraph exams have been in use for over 75 years. During that time approximately 250 studies have been conducted on the accuracy of polygraph tests. Since conditions and factors involved in research will vary, and since a polygraph examination is a very complex process, it is difficult to extract a precise accuracy figure from the data. Nevertheless, the preponderance of available information indicates that the accuracy of a properly trained examiner, utilizing established testing procedures, is around 95% for specific-issue investigations.

While the polygraph technique is not infallible, research clearly indicates that when administered by a competent examiner the polygraph test is the most accurate means available to determine truth and deception.

 

Are Polygraph Exams Admissible In Court?
 

Contrary to popular belief, polygraph results are admissible in most courts across the country. The Supreme Court has yet to rule on the issue of polygraph admissibility so it has been up to individual jurisdictions to allow or disallow them. There are some jurisdictions that have bans on admitting polygraph results, but most allow them if both the plaintiff and the defendant have agreed (stipulated) that the results of the test will be admissible prior to the examination being conducted.
 

Are The Results And Information Confidential?
 

Yes, we at Ventura Polygraph hold ourselves to very strict confidentiality and privacy standards. All information from an examination is kept strictly confidential and private except for PCSOT examinations where the results are reported to the Treatment Provider and the Supervising Official.
 

Are There Errors In Polygraph Examinations?
 

(The False Positive & the False Negative)
 

While the polygraph technique is highly accurate, errors can occur. Errors are usually referred to as either false positives or false negatives. A false positive occurs when a truthful examinee is reported as being deceptive. A false negative occurs when a deceptive examinee is reported as truthful. Since it is recognized that any error is damaging, examiners utilize a variety of procedures to identify the presence of factors which may cause false responses, and to insure an unbiased review of the polygraph charts.

These include:

• An assessment of the examinee's emotional state.

• Medical information about the examinee's physical condition.

• Specialized tests to identify the overly responsive examinee and to calm the overly nervous.

• Utilizing only validated testing formats and protocol.

• Factual analysis of the case information.

• A thorough pretest interview and a detailed review of the questions.

• Quality control reviews.
   

(Inconclusive or No Opinion)

An inconclusive or no opinion result simply means that insufficient data is available for the examiner to render a definitive opinion of deception indicated (DI) or no deception indicated (NDI). In such cases a second examination is usually conducted in an effort to arrive at a decision. The classification of a polygraph examination as "inconclusive" protects the examinee from being falsely identified as deceptive when inadequate data is collected. Critics of polygraph have wrongly classified inconclusive test results as errors. In actuality, a determination of inclusive is made to avoid errors in identifying truthfulness or deception of an examinee.
 

Do Outside Factors Influence The Outcome Of A Polygraph Exam?
 

Professional polygraph examiners take specific steps to mitigate circumstances that may affect the results of the exam. They also take outside factors into consideration when administering the test and analyzing the data to eliminate factors not related to the examination.

Can A Person Fail A Polygraph Because Of High Blood Pressure Or Nervousness?
 

No. While a person's heart beat and respiration rate may increase when he or she is nervous, a qualified examiner understands this and will take it into consideration when evaluating an examinee's response. Unlike general nervous tension, an examinee's deceptive responses is highly specific. An examiner mitigates a nervous response by reviewing the questions with the examinee and through an acquaintance or "practice test" prior to the exam.

Source: American Polygraph Association