Conduct of Polygraph Examination
Polygraph examinations are generally conducted in four phases:
- Phase I: Preliminary Preparations
- Phase II: Pre-Test Interview
- Phase III: Examination Proper
- Phase IV: Post-Test Interview or Interrogation
Phase I: Preliminary Preparations
This phase sets the stage for the initial contact between the examiner and the subject. While the polygraph has not yet started running nor has the components been attached to the subject, the test has already started.
During this stage, the examiner would collect information and evaluate facts. The investigator is expected to provide the as much of the following to the examiner:
- Sworn statements of the suspects, witnesses, victims, or complainants
- Incident or spot report, background information of the persons involved
- Rough sketches or pictures of the crime scene and other facts such as articles and exact amounts stolen, in cases involving property theft
- Peculiar aspects of the offense
- Exact time the offense was committed
- Known facts about the suspect’s action or movement
- Facts indicating any connection between the persons involved
- Exact types of weapons used
- Laboratory test results
- Unpublished facts of the incident known only to the victims, suspects, and the investigator
Preliminary Observations
As mentioned, the test already started as soon as preliminary prep started. During this time, the examiner is already making observations of the subject’s behavior and everything is being recorded by an assistant or a receptionist. While in the waiting room, the subject’s conduct and behavior are also being observed and recorded.
Phase II: Pre-Test Interview
During this phase, the examiner interviews the subject to prepare them for the test. Additionally, the examiner must make sure that the subject is made aware of their rights as subject of a polygraph examination.
The examiner must ensure the following:
- That the subject is appraised of their constitutional rights
- That the subject gives their written consent to be subject of the polygraph examination
- That the subject’s personal information is taken
- That the subject is confirmed a suitable subject of a polygraph examination
- That the subject is psychologically prepared
- That the subject is informed of their involvement in the case
Specifically, the subject must be clearly informed of the following:
- That they have the right to remain silent
- Anything they say may be used in favor or against them
- That they have a right to a lawyer of their choosing
- That they have the right to refuse the examination
The following steps have been found to be an effective pre-test interview procedure:
- As the examiner enters the waiting room to request the subject to accompany them into the examination room, the examiner should extend a cordial, but firm greeting to the subject.
- Upon entering the examination room, the subject should be requested to sit down in a chair beside the instrument. Immediately afterwards, the examiner should proceed to the taking of the consent of the subject.
- The examiner should then fill out the necessary data in the interrogation log.
- Afterwards, the examiner should ask the subject whether they have previously undergone a polygraph examination. No further comment should be made by the examiner, but they should listen carefully to whatever the subject may say.
- If the subject was not made aware of the purpose of their appearance at the testing laboratories, the examiner should explain that they are being asked to undergo a polygraph examination as part of the investigation of the case in which they are involved.
As much time as necessary should be spent on preliminary interviews.
Phase III: Examination Proper
After the pre-test interview and the subject is confirmed to be qualified to take the polygraph examination, the examiner should proceed to the placement or attachment of polygraph sensors. They should be attached in the following order:
- pneumograph
- cardiosphygmograph
- galvanograph
The instrument is attached to the subject thus:
- The blood pressure cuff is wrapped around the subject’s upper arm or bicep and the pneumograph tube is adjusted around the chest and abdomen.
- The cuff is then inflated to a point approximately midway between the systolic and diastolic blood pressure.
- The synchronous motor carrying the paper upon which blood pressure, pulse, and respiration recordings are made is then set into motion. The paper moves along the rate of six to 12 inches per minute. Then, 10 to 15 seconds after the instrument has been started, the inked-filled pens of the instrument starts recording. (This step will only apply when using analog polygraph machines.)
Once the instrument is properly attached, the following should be done:
- The subject is informed that the test is about to begin.
- The subject is informed that they will be asked several questions which should be answered by “yes” or “no” only, and that these questions are brief and straight to the point. They must be discouraged from making any unnecessary movements or making any comments or statements.
- After the instructions are given, the examiner must wait five to 10 seconds before asking the first question so that standard tracings may be made.
- The rest of the questions will be asked at an interval of 15 to 20 seconds. The test should be completed in three to four minutes.
- Three charts should be obtained, with a rest interval of five to 10 minutes between each test. This is done to meet the requirement in chart interpretation that a specific response must appear in at least two charts.
- The examiner should pay attention to the subjects reactions and movements during questioning. These should all be recorded in the chart, and the subject should be reminded not to move too much if they are doing so.
- If the subject refuses to take the test, it should be terminated. This type of behavior indicates a dishonest subject.
- The examiner will interpret the graphs and prepare the examination report.
Note that examiners may write their questions in advance or create them in the course of the test during intervals between questions.
Phase IV: Post-Test Interview or Interrogation
Once the test is completed, the instrument is turned off and the examiner makes a determination whether the subject is deceptive.
Should the subject have been deceptive, the examiner will proceed to conduct a short interrogation to try and elicit a confession. Otherwise, the examiner should simply release the subject and thank them for their cooperation.
If further questioning is conducted, it must help:
- Clarify findings on the graphs
- Understand the reasoning behind the subject’s deception other than knowledge of the crime
- Obtain additional information that might help further the investigation
Sample Forms
