Posted by arlene

How Legal Wire tapping Works

CALEA requires that communications providers allow law enforcement officials to be able to listen in on phone conversations and get information about those phone calls, but only when the law enforcement agency has gotten approval for the tap.

The law enforcement agency goes before a judge and presents reasons a wiretap is needed. If the judge approves, a legal document or order is delivered to the communications provider.

A specially authorized person at the communications provider logs in to a system specifically set up for CALEA-approved wiretaps. A number of systems are sold by various manufacturers, but all of them tap into the routers and switches that make up telecommunications networks.

All calls on the communications network are routed digitally over switches and routers. The system used for taps connects to a central point in the network, over which all communications travel.

The tapping system captures two primary pieces of information about the call—the actual voice transmission itself (often referred to as call content information [CCC]) and data associated with each call, such as the phone numbers at both ends of the call (often referred to as call associated data [CDC]).

The CCC and the CDC information are sent over special secure routers to the law enforcement agency.

The Federal Communications Commission has ruled that PC-to-PC calls, when a call is made directly from one computer to another over the Internet using Voice over Internet Protocol (VoIP) software such as Skype, is subject to CALEA. But as of this writing, no technical way has been devised to tap in to those calls.

How Lie Detectors Work

The two general types of lie detectors are analog detectors, which are older technology and are not frequently used today, and digital lie detectors, which are newer and are the most commonly used type of lie detector.

When someone is given a lie detector test, various tubes and wires are attached to him to measure his physiological responses to questions. To measure the respiratory rate, two rubber tubes filled with air (called pneumographs) are put around the person’s abdomen and chest. As the chest and abdominal muscles expand, it displaces air inside the tubes. A lie typically results in a higher respiratory rate.

In an analog lie detector, the tubes are attached to a bellows, which in turn is connected to a mechanical arm. That arm is in turned connected to an ink-filled pen that records the respiratory rate on scrolling paper.

In a digital lie detector, a transducer converts the measurements of the displaced air into digital signals that are fed into a computer. The computer uses that information to calculate the person’s respiratory rate.

To measure blood pressure and heart rate, a blood-pressure cuff is applied to the person’s upper-right arm. Tubing goes from the cuff to the lie detector. In an analog lie detector, the tubing is connected to a bellows, which is connected to an ink-filled pen that records the blood pressure and respiratory rate on scrolling paper. In a digital lie detector, a transducer converts the information into digital signals that are fed into a computer. The computer uses that information to calculate the blood pressure and heart rate. A lie typically results in higher blood pressure and a higher heart rate.

Galvanic skin resistance (GSR), also called electro-dermal activity, is in essence a measurement of the amount of sweat on someone’s fingertips; it is measured as well. The theory is that when someone is placed under stress, he sweats more. Galvanometers are connected to two of the person’s fingers and measure the ability of the skin to conduct electricity—the more sweat there is, the better the skin conducts electricity. In an analog lie detector, the fluctuations are recorded on scrolling paper, while in a digital lie detector, they are recorded in the computer. A lie typically results in greater GSR.

The examiner running the lie detector tests asks the subject a series of questions. He asks control questions, as well as questions relevant to the crime being investigated. The control questions are general questions that the examiner uses as a baseline against which he will compare answers to the questions about the crime.

After the test is complete, the examiner interprets the results and reports on whether the person lied about answers to certain questions.

Lie detector results can be misinterpreted, and people can use techniques to fool the test—for example, taking sedatives before the test, putting antiperspirant on their fingertips, and other measures. Because of this, test results are usually not admissible in court, except under very strict guidelines.

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