No.
I am not familiar with all California law but I would say the answer to this question is yes. A police officer can answer your cell phone, but, they may not search (look at contacts etc.) without a warrant.
A warrant is a court order that allows police to perform an action, like search a home or obtain a person's phone records. The government should not be able to wiretap phones with a warrant to do so. Otherwise, the government is violating the privacy of innocent citizens.
It's illegal to do that anywhere!
The police tap the phone of a suspected criminal without a warrant.
a person can, whether they should or if its legal is another matter.
If they have a warrant, there's really not much you can do. Everything you do on your phone is logged with your carrier, so they can get those records from your phone service provider.
Well, if the police department thinks that a cell phone may hold important evidence, then there is no need for a warrant. By the time the warrant is issued, the evidence may have been already destroyed or deleted.
With the proper warrant or probable cause, a cell phone could certainly be searched. More commonly the police would obtain necessary records from the cellular service provider.
Only if they have obtained a federal wiretap warrant from a federal judge.
A search warrant is a different type of warrant, BUT with a specific phone tap warrant the police can listen in on your phone calls. Be aware however, that "cordless" and cell phones, operate on public radio frequencies assigned by the Federal Communications Commission. ANYONE, with the proper equipment to do so, can listen to these conversations.
The text messages are stored on the network's computer - NOT your phone. They are simply downloaded to your phone when they're received. The police simply need to serve a warrant on the company, to have them print out your messages. The don't need your phone !
The cell phone company and its employees will look at your records. Once the records are sent to you, you don't have to share them except when required by a court, such a in discovery in an on going lawsuit, or pursuant to a subpoena or warrant.