Here in the Seattle area, DUI checkpoints are (happily) either non existent, or so rare I have neither seen or heard of one -- so pardon my ignorance.
Question: For those areas that actually do this kind of stuff regularly - Is it common practice to actually have the calibrated breathaylzer machine on the scene at the checkpoint? I'm not talking about the small portable device the officer can stick in your window... but the actual "intoxalyzer" machine usually found back at the station.
Good men must not obey the laws too well.
~Ralph Waldo Emerson
Any fool can make a rule, and any fool will mind it.
~Henry David Thoreau
Remember always: The government is not the country!