Body Language

• A person's body language can tell a police officer whether she is lying. According to an article in IntelliHealth.com, Dr. Alan Hirsch, someone who is fidgety and sweating profusely exhibits a much stronger clue of giving false information than someone who is sitting still and appears to be calm. Sweating is an involuntary reaction, so this can be an indicator. Others may have a nervous habit that can indicate when they are lying, such as twisting their hair or wringing their hands. However, body language should not be used as the only indicator as it is also a legitimate sign of nervousness in general.
  
  

Details

• Someone who is lying during an interrogation will often describe details vaguely or not include them at all, according to Forbes.com. The suspect is hoping to remove suspicion by showing how little he knows about what happened. However, police officers are trained to dig for details. The officer will ask questions, leading the suspect to continue to give more details. The more details he gives, the more likely he will get caught in a lies.
  
  

Emotions

• When a suspect is being interrogated by police officers, her emotions and reactions are watched closely. Blifaloo.com reports that a lying suspect often knows what emotions she should be feeling in a given situation and forces these emotions through. As a result, the reaction time is typically too fast or too slow compared to the reaction time of genuine feelings. A lying suspect also tends to exaggerate the emotions, holding on to the visible reaction too long and then abruptly returning to normal. Agitation is a common emotional sign of lying. Officers also watch facial expression as a forced facial expression uses far fewer muscles than a natural one. A genuine smile lights up the whole face, while a force one only involves the mouth.
  
  

Physical Interaction

• Someone who is lying may have difficulty looking his accuser in the eye, Hirsch says. His eyes may dart around the room while he is answering the officer's questions or he may focus on a spot above her head instead of looking directly at her. He may also physically turn away. Bifaloo.com adds that a suspect who is lying is more likely to go on the defensive, taking a defensive stance, such as crossing his arms and remaining stiff, rather than an innocent suspect who will be on the offensive, such as sitting with open posture and moving freely.
  
  

Verbal Cues

• Some verbal cues are subtle, and someone who is not trained to pick them out would think nothing of them. However, trained police officers hear these cues and know someone may be lying. For instance, the use of contractions is a more normal way of speaking. Someone who is lying is more likely to not use contractions, seemingly for emphasis. For instance, she may say "I did not do it" instead of "I didn't do it." Someone who is lying may also use a longer answer than necessary, speak in a monotone voice, garble words or give an answer not directly related to the question and change the subject. He is also more likely to pause while telling a story to get the details straight.