What do law enforcement look for to determine “probable cause” on suspicion of DWI?

Q: What do law enforcement look for to determine probable cause on suspicion of DWI?

A: Law enforcement will look for violations of traffic laws, for example, swerving of your vehicle, or crossing the center line, or crossing the fog line, or speeding, or any kind of erratic driving. Once they stop you, they look for typical signs of intoxication: glassy eyes, slurred speech, that sort of thing. So that is what they are going to be looking for. In addition, if they give you any of the field tests, and, for example, you are not able to stand on one leg, or your eyes move when a pen in placed in front of your eyes, or you can’t recite the alphabet, that sort of thing. They look for all sorts of indicators that you are impaired—that in other words, you are in some way influenced by alcohol to the point where you shouldn’t be driving.