In a DUI prosecution motions are often made to suppress or exclude evidence obtained by the police pursuant to Penal Code 1538.5. Commonly in DWI cases the defense would like to have the bllod test thrown out because the cops failed to explain the choice of tests, ie. breath to a suspect. A Motion to suppress results of blood test (or evidence of refusal) on the ground that the police denied the defendant a choice of tests may not be the appropriate vehicle. Indeed, a Penal Code §1538.5 motion has been held to be improper because the denial of a choice of tests may violate due process but does not violate the Fourth Amendment; common law suppression motion is proper method for challenging due process violation. Similarly, a motion to suppress a statement on Miranda or voluntariness grounds cannot be brought under Pen C §1538.5, but a motion to exclude a statement on the ground that it is the result of an unlawful detention or arrest falls within Pen C §1538.5. The underlying principle is that Pen C §1538.5 motions are limited to those that make a Fourth Amendment claim, subject to rare exceptions.
According to a prominent local Kern County DUI Lawyer, The district attorney has the burden of proving the validity of a warrantless search or seizure, after the defendant has established that there was no warrant, as is often the case in drunk driving prosecutions. The defendant has the burden of proving the invalidity of a search or seizure under a search or arrest warrant. The standard of proof is a preponderance of the evidence.