You even see it at Qualification shoots, with no stress other than the possibility of a re-shoot, some guys and gals get geeked, amped up, have an adrenalin dump or to put it in scientific terms - experience a SNS (Sympathetic Nervous System) response. The result is that they enter the tunnel of limited thought and perception. What once was a big 360 degree world has now shrunk and even on the firearms training range their decision making is limited, peripheral vision is gone and performance deteriorates. That's just in training on the one way range (with no suspect shooting back...). This is not a good thing on the range (my partners and I have had officers turned toward us with loaded pistols) but limited vision and decision making on the street is even worse.

So focused, so intent, so tunneled in on the rear bumper of the fleeing suspect's vehicle you fail to see citizen's vehicles (with the right of way) headed toward the intersection you're barreling toward. So hyper-attentive to the suspect in front, you fail to see his accomplice on your flank. So intent on making your Electronic Restraint Device work on the resisting suspect that it has become your only plan, so you press the trigger again and again despite the fact it simply isn't working. All of these things are examples of the effects of the SNS response on your perceptions and cognitive abilities such as decision making.

The antithesis or opposite of the examples given above is the officer that shoots a high score on the Qual events in minimum time while exercising sound tactics or the cool-as-a-cucumber officer that has complete composure (even sounds calm on the radio) while the world around him is in violent chaos.

The Difference

I would submit that the difference between composure and loss of control is both mental as well as physical. I've known of officers that had multiple crashes after just receiving emergency calls - fights, man with gun, burglaries in progress. They simply could not handle their body's reaction to an SNS response. All of a sudden the radio call from dispatch started the cascade effect that is the Sympathetic Nervous System reaction including tunnel vision, auditory exclusion (tunnel hearing) and limited cognition and - blammo they're turning in front of another motorist or doing something reckless act like driving too fast and cause an accident.

The mental component is multi-fold: