Biometrics cues are uncontrollable bodily reactions to some type of external stimulus. These uncontrollable reactions are caused by the limbic system. When the limbic system perceives something as a threat it sends out a rush of hormones and chemicals that will have an affect on our body. As we get older we start to recognize some of these effects and associate them to emotions. If someone is mad you would expect to see flared nostrils and reddening of the face because that individual is preparing for the freeze, flight or fight response. The more an individual has to hide their true emotions, the more that individual will stand out. Theses are just a few indicators you would see amongst others that would be very easy to see as well. To the trained observer you can pick up on not only body language but biometric cues as well.
Just a few weeks ago we went on a trip to Hawaii. I loaded the plane and took my seat when I saw this man sitting across from me. He was screaming on the inside that he was not comfortable with flying. As I observed him he was sweating profusely, he had already asked for a drink before we even took off. I picked him out as an anomaly because I have a baseline for a plane. I have flown enough to know that people are generally comfortable and relaxed when they get on a plane. You should expect to see people boarding the plane and looking for their seats. When they find their seats they put their bags up in the overhead bin and take their seats. Once they take their seats they strap in and either chat the person up next to them, put on some headphones and listen to music or start to read a book.
Then there was a heavyset man who took the seat right next to him. At this time the individual I pegged out as an anomaly started to turn red in the face and breathing heavily. I could not see his entire face but I would assume that his nostrils were also flared. He also began to clench his chair and move around the chair nervously. At this point I knew that he was not only uncomfortable but that he was pissed off. This went on until the plane was completely boarded. Once he recognized that there was an open seat he immediately moved over to that seat. When he got to the seat he went back to his baseline of being uncomfortable and just sweating profusely. All of the other biometric cues began to go away and he was going back to his norm, which was breathing hard and sweating profusely. When the plane began to take off he started to breathe harder and clenching his seat. Once we were in the air he began to slowly calm down and finally went to sleep.
As long as you have a baseline for an environment you will be able to identify the anomaly. So the baseline for a plane should be calm, collective, organized and for most people internal. Anything outside of that should be observed and ultimately prompt you to make a decision.