Daysleeper,
I don't know about the US, but in the UK you wouldn't get a blood test.
The point I was making was that there is a second breath test at a Police Station on a Calibrated machine (its the size of a kitchen unit) and that provides the evidence in the form of a print out of the amount of alchol in your blood (apparently its proportional to the amount in your breath hence the test is done on breath).
There is no blood or unine test because they are not needed. The calibrated machine in the Police Station is tested to make sure there is nothing that will mess with it.
So in the UK its not 48 hours, its less than 48 minutes.
As I said I don't know about the US, I would assume that they are at the same level of development as us, and therefore they use the same sort of machine. Thats an assumption based on the fact that this pilot is appearing in court today. If there was no read out of his blood/alcohol level there really wouldn't be much point in him appearing in court at this stage. However I am willing to be shot down on the last point by someone who does know something about the US Judicial system.