Legal Question in DUI Law in California

You are arrested when you are no longer free to leave. It doesn't necessarily mean that you have to be handcuffed or have your rights read. It means the arresting agent (police officer, etc.) is exercising his authority to deprive you of your liberty to leave.

Handcuffs make it official.

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Sometimes, and for some legal purposes, a cop will try to create ambiguity about whether or not you are free to leave. For example, in order to use statements a defendant makes in a "custodial interrogation," the cop must first read Miranda. If the cop claims you were never in custody, the judge might admit whatever you foolishly blabbed to the cop into evidence. It is always a good idea to politely ask the cop if you are free to leave if there is any doubt.

Q: We're letting our drug-sniffing dog out for some exercise, do you mind if Fido here sniffs your car?

A: Officer, I'd really like to get going now.

or

Q: Am I under arrest?

A. What makes you think you are under arrest?

Q: Can I go now?

Neither handcuffs nor "not free to leave" equals an arrest. Custody - more than just being detained (where you're temporarily not free to go) is the defining factor in an arrest. The police can use handcuffs in order to keep you there during a detention and that does not automatically make it an arrest.

Miranda rights are required when you're in custody and being interrogated. You don't necessarily have to be arrested to be arrested, but "in custody" for Miranda purposes means you're the functional equivalent of an arrest (or actually arrested).

So - to answer your question - neither handcuffing or Miranda warnings indicates an arrest. There's more to it.