Movement
Excessive or dormant eye movement beyond an established baseline can indicate escalation. Flitting eye movement, back and forth, up and down, is perhaps the easiest cue to identify. Baseline eye behavior is steady, makes eye contact, breaks away and comes back to contact in a relaxed unattended cadence. Behavior beyond this baseline can be indicative of many things including being under the influence, but they're a dead-ringer for escalating behavior.
Eye movement that goes to specific areas in the physical context can be indicative of a hidden something the subject does not want to be discovered. This is called indexing. The eyes move to a specific location on the couch and then back to you and then back to the couch indicates significant psychological noise on the subject's part about whatever may be stashed in the couch cushions and their fear that you may find it. Eye indexing to the door could be indicative of thoughts of escaping. Indexing to your utility belt means it's time to step away.
Chances are you've played the stare-down game, blinking chicken as it may be, the one who blinks first loses. This is instinctive, the Alpha-male stare, and is indicative of either a power play on the part of the subject (and the LEO) and/or your subject has made a decision to take the escalation to attack.
There are many more identifiable eye movements, but flitting, indexing and the Alpha stare are the three most common and easily identifiable as escalated tells. But you know that already.
Eye Lids
Blink rates can indicate escalated anxiety or controlled contempt and a range of emotions in between. Normal blink rates range from two to ten times a minute depending on relative humidity and eye moisture. Blink rates decrease when the eye is engaged in reading or watching a screen, down to three to four times a minute.A blink rate baseline can be derived by counting blinks per minute at resting or non escalated levels. More accurate blink rates are determined over a period of time, averaging blink rates from at least a half dozen samples. But during a call, you don't have time for that.
Increased blink rates in a subject can be a result of escalated anxiety, emotion, or result from excessive eye movement. Decreased rates stem more from the Alpha-male stare or the inherent decoy from being detected in a lie or escalation.
Closing eyes, blinks that last seconds, are also indicative of escalation. From being as simple as, "If I close my eyes this will all go away," to eliminating the visual channel to better envision and plan the eminent attack, the closed eyes cannot be dismissed as some kind of tick or nervous reaction.
Remember, a baseline is critical. Nothing has meaning by itself. Relative humidity, contact lenses, fatigue, alcohol, weed, meth, wind conditions all skew the baseline. When making the initial subject encounter, use this first zone to assess baseline at contact and watch how the subject departs from it.