When an officer pulls a driver over in the dark evening hours, he or she is on the alert to see if the driver is under the influence. He or she begins observations when approaching the car.
As the driver rolls down the window, the officer is checking to see if the driver smells of alcohol, if the eyes are watery or bloodshot, if the driver is having trouble retrieving his or her license, and if the driver's speech is thick or slurred. If the officer does not have reason to believe the driver is under the influence, he or she must allow the driver to drive off. The officer cannot order the driver out of the car to complete the field sobriety tests unless he or she has probable cause to continue the investigation.
Smell of alcohol
The smell of alcohol may be in the car even if the driver is not the one who's been drinking. If there is a passenger, the passenger may have been drinking. If the driver has been in a bar, he or she most likely smells of stale cigarette smoke and alcohol, even if he or she had nothing to drink.
Blood shot, watery eyes
Blood shot, watery eyes may have several causes. The driver may be operating on very little sleep, may have worked all day at a computer terminal, may be suffering from a cold or allergies, or may look as he or she always does. Remember that the officer has never seen the driver before and has nothing to compare his or her observations to.
Trouble with finding the license
People organize wallets in many different ways. Some don't separate their credit cards from their driver's license. And some people couldn't find their license if they were stone sober in broad daylight. This factor alone says nothing about the driver's state of sobriety.
While an officer may associate slurred speech with driving under the influence, it may also be a side effect of certain medications or medical conditions. Remember the officer has never spoken to the driver before and therefore, has no idea how his or her voice "should" sound. If the topic comes up in court, the officer should be questioned on how many other times he has spoken to the driver (none) and how the driver's voice was different from his or her usual speaking style.
While the officer may assert that some or all of these factors are indicative of intoxication, an experienced attorney knows there may be an innocent explanation.