Under California DUI law, you are currently considered to have given "implied consent" to a DUI chemical blood or breath test if you drive a car in the state. If you refuse to take such a test after being lawfully arrested for DUI, and you are later convicted of DUI, you will face additional penalties for chemical test refusal.
A very recent holding by the Supreme Court of the United States suggests that this law may be unconstitutional where DUI blood tests are concerned. In Birchfield v. North Dakota, the Court overturned laws in effect in several states that make it a separate crime for people arrested for DUI to refuse blood tests if the officers ordering the tests don't have warrants for them.
According to the Supreme Court, these laws violate defendants' Fourth Amendment rights. This is because people have a strong privacy interest in avoiding unwanted blood tests.
However, the Court did not believe that this reasoning applies to DUI breath test. They stated that there is less of a privacy interest in avoiding a breath test--and thus that it is perfectly constitutional for officers to require people arrested for DUI to submit to a breath test or face criminal penalties.
Applying this reasoning to California's DUI chemical testing laws could lead to a conclusion that DUI suspects may no longer face chemical test refusal penalties if they refuse a blood test. Officers would be required to get a search warrant from a judge before they could order an arrestee to take a blood test under threat of criminal sanctions.
But California's law is different from the ones considered in Birchfield because it does not make refusing a chemical test a separate crime. Instead, it imposes additional DUi penalties for test refusal. So it is not clear that Birchfield applies to our state's laws.
Even if it does, it may not make much of a difference to most DUI suspects, since officers can simply administer a breath test instead.
The Birchfield is likely to matter most in cases where the officers suspect that a driver is DUI of drugs. In those cases, there is more of a chance that officers will push specifically for a blood test.