GENERALLY, if police have a reasonable suspicion (such as a phone call), you need to provide ID. However, it’s NOT clear in California. See #41
http://en.wikipedia.org/wiki/Stop_and_identify_statutes
“The California Peace Officers Legal Sourcebook (”CPOLS”; written by the office of the California Attorney General) maintains that failure to identify oneself does not constitute a violation of California Penal Code §148(a)(1), resisting, delaying, or obstructing a peace officer:
Unlike Nevada and 20 other states, California does not have a statute mandating that a detainee identify himself, and that obligation cannot be read into Penal Code Section 148. (Rev. 1/08, p. 2.14a)”
*Even the ACLU says it’s best to give them your ID.*
Not exactly. In many states, you may be required by an officer to identify yourself in such circumstances, but that just means that you have to give your name, and in some states, your address. It does not mean that an officer can (legally) require you to show an ID card. The Supreme Court ruled on that quite some time ago. There is no requirement to carry an ID in this country — outside of when driving, etc. — so obviously there can be no requirement to show ID.