If you refuse a roadside sobriety test,they can and will and do arrest you, tow your car.
I assume if you refused a blood test, same thing, do not know the law about it, or how the law varies from state to state.
Usually the normal coercion is involved: Take the test or be arrested for DUI.
Cal. has an implied consent law, which means you are presumed as a condition of the privilege to drive to have impliedly consented to chemical testing.
Blood tests are a natural progression of the already accepted ( and highly unreliable ) breath tests.
Each one degree of body temperature above normal will cause a substantial elevation (about 8%) in apparent BAC.
Doesn't matter if DUI arrest is later declared invalid, you are out your car, tow fee, lawyer fee, and maybe even insurance points.
Personally, if I were a radical, I would chug a beer in front of the officer after i had been stopped.
( Again, i am NOT supporting drunk driving, I am against creeping police state tactics).
One could argue being forced to give incriminating evidence is unconstitutional.
edited to add this:
Each one degree of body temperature above normal will cause a substantial elevation (about 8%) in apparent BAC.
http://www2.potsdam.edu/hansondj/DrivingIssues/1055505643.html