Diurnal rhythm of alcohol metabolism

Why is breathalyzer a poor method of measuring blood alcohol levels for purposes of DUI tickets? Ed Brayton explains and links to DUI Blog with additional information.

Also, do not forget that every function in the body exhibits a circadian cycle. Likewise, alcohol metabolism:
This is from an old study, from the times when it was OK to recruit some college freshmen to drink alcoholic beverages in the name of science. This is a record of a diurnal rhythm in alcohol clearance, I believe (I cannot find the original paper I swiped this image from a long time ago).

It shows why we can drink more in the evening than at other times of day. You can save some serious money by downing a single shot at dawn, according to this graph.

So, at what time of day/night did the cops stop you to give you a breathalyzer test?