READ: Interrogation

Interrogation

Interrogation

During an investigation, it is usually necessary to question witnesses and suspects. Sometimes this process begins at the scene and this information is included in initial police reports. Suspects, people of interest, witnesses, and others related to the crime may be brought in for questioning. This process is often vital in determining the outcome of the case, but the information gathered during questioning is only useful if investigators can be sure the person was not lying. The ability to detect lies is something that interrogators are trained to do. Lie detection can be accomplished through polygraph machines, facial expressions, body language, and analyzing what the person says.

Polygraph Machine

The polygraph machine is also known as a lie detector test. A polygraph machine works by monitoring several different signals from a person who is being questioned. Sensors are place on the person who is being questioned. These sensors detect things such as breathing rate, heart rate, perspiration, and the person’s pulse. The interrogator will begin asking questions and the polygraph machine will create a graph of these signals during questioning. A trained interrogator can read the graph during or after the questioning to identify if any significant changes happened during specific questions. For example, if the breathing and heart rate increase it could indicate that the person is lying.

Reading the graphs from a polygraph machine takes training and experience, but a trained interrogator can detect lies with a high level of accuracy. Polygraph results are not always totally accurate because people respond differently during lying, and the results are based on the interpretation of the interrogator. Even though polygraph tests are not foolproof they are a useful tool in an investigation.

Body Language

Body Language and Facial Expressions

Interrogators may also look for body language or facial expressions that indicate that someone is lying. People who are lying will also speak in specific ways or use certain types of words. It takes training, but by using these subtle cues investigators can determine if someone is possibly lying. Just because someone seems to be lying doesn’t prove they are. Investigators will often use this process to catch a person in a lie and get a confession. Click HERE and read the infographic to learn about what signs an interrogator looks for.

Signs of Lying

In the video below, a retired fbi agent shows some of the things to look for to tell if someone is lying:

The video below shares some more tips about catching liars and some of the techniques used in interrogation: