"Lie detectors" have become quite real helpers in the field of inquiry. According to their creators, they should identify whether the truth says the suspect is the subject or not. This is very important in the conduct of interrogation in the investigation process.
Investigative experience shows that lies and denials criminals in the interrogation associated with various physiological phenomena. First of all, the increase in blood pressure, changes in the moisture content of the skin, and uncontrolled slatinany of saliva, dryness in mouth, deep breaths. These phenomena have been used by physiologists and psychologists for the development of the polygraph . or "lie detector". The first experiments in this direction were initiated in the 90-ies of the last century, modern electronic devices allow you to properly evaluate the responses in 85 cases out of a hundred.
"Lie detector" consists of a set of sensitive measuring devices that are connected to the following sensors: elastic bracelet, fastened above the elbow, giving the movable tape recording changes of heart rate and pressure of the system placed at chest level, to transfer and record the breathing rhythm and electronic devices for measurement and recording of changes in skin resistance electrodes which, having the form of bracelets, are fixed on the hands given. Speed paper tape when recording is 160 mm per minute.
The study is based on a series of questions that must be answers like "Yes" "no" (denoted on the chart recording + or -). First, questions are asked on extraneous issues to determine the normal reaction is "innocent," then the issues associated with the investigation, h while observing the deviation of the shape of the recorded curve from the norm. It is shown in Fig.1.
Fig.1. Entry signals "lie detector":
as a result, innocent questioning, the suspect in the theft of money;
b - record reactions of the offender (questions 1, 2, 5-not connected with the investigation,
3 - if he knows who took the money?" 4-"For whom he stole the money"?
(see the response to questions 3 and 4); x-the blood pressure;
u - skin resistance; g-breath.
An additional test of character reactions of the person is the experience of playing cards. Researched show 10 different cards and offer to remember one of them, and then shuffled them, spread out for each other. The person questioned should answer every time is "no", i.e. once he is lying. It will be registered on the record and will serve for the correct decoding of subsequent entries. So basically does the work of lie detector, which in many cases allows you to isolate the main culprit, accomplices and those who knew about the crime. However, only on the days the results of decoding of the polygraph records cannot serve as evidence against the accused before the court. However, in the U.S. lie detectors are 19 large state institutions (including the army, police and the FBI), who in 1964. had 512 such devices. During the year, with the help of lie detectors to explore 20,000 people. Many such devices used in private firms, such as banks. The fairness of the banks ' staff regularly checked with the help of lie detectors. Firm that makes lie detectors organizes semi-annual training program for the personnel operating the detectors. It includes psychology, law and other subjects.
A simplified lie detector (Fig.2) has such high sensitivity that already with occasional mild agitation investigated or in cases of intentional lies the meter pointer is deflected. Here is a sample of readings (in µa) in response to expressions, emotive and indifferent: kissing - 73, love - 59, matrimony-58; carrots - 18, flower - 16, pencil-15. Symbols: And - to the electrodes In the device to record, etc.
Fig.2 a Simplified version of the "lie detector".
Transistors - KT3102 and CT (corresponding conductivity)
Two electrodes (Fig.3), which have the appearance of closed loops of wire without insulation, fastened to the hand or wrist. The former provides greater sensitivity, but there may be interference caused by movements of the hands. If so, then the electrodes should be fixed on the wrist. If the sensitivity is insufficient, connect among themselves two or three loops in parallel. Loop attach to the skin of a rubber or rubber tape or just a bandage. The electrodes can be fixed and the sole of the foot.
Fig.3. Conventional electrodes.
The resistance of the skin, which under normal conditions is up to 3...100 K, under the influence of the excitation is changed to 5%. The device displays information about it in 1.7...2.4 GHz with after exposure to light, sound or pain signal.
Fig.4. Universal electrode.
(1 - can be paper from packaging, photographic film, medicines, etc.);
foam rubber should be soaked in an aqueous solution of salt.
The sensitivity of the device ( Fig.2) is regulated by a variable resistor R1. To the output terminals, in addition to the galvanometer, you can connect the recorder. You can also add operational amplifier with relay or actuator, or connect the device to the input of a radio telemetry system. Resistors R serve only to protect the transistor against overload and short-circuit at the input of the system or in moments of turning on the power supply.
The device may find other uses, for example in the technique in studies of processes with flow sensor in the frequency range from thousandths of Hertz to tens of kilohertz.
At leisure with the device can spend a fun "measurement of temperament." On the fingers of partner and partner strengthen spring metal clips. In the moment of the kiss the meter pointer is deflected, touching another subject will give a different result.
It is interesting to try to apply this device as a lie detector. For this purpose, the metal clamps fixed on the index finger of the partner and asking him questions, watching the readings of the galvanometer. The range of questions can be expanded, for example: "what's your name?" "Where do you live?", "Do you drink wine?, "Smoke?", "What were you doing Saturday night?". Before measurement should be zero. Both clips should be already fixed. The device it is desirable to have a bilateral scale.
Literature
Publication: N. Bolshakov, rf.atnn.ru