http://www.nolo.com/legal-encyclopedia/police-questioning-miranda-warnings-29930.html

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You don’t ever have to be given your Miranda warnings. An officer can arrest you for a traffic-related offense or for murder, and he doesn’t have to read you your rights. You can be booked, arraigned, and convicted without ever being read your rights.

As long as your confession isn’t needed or wanted, there is no need to warn you against self incrimination. The only time Miranda is required would be if you were subjected to custodial interrogation (meaning you’ve been taken into custody and are not free to leave). And if you are not read your rights when you were entitled to them, the only consequence is that any confession you made couldn’t be used against you during your trial as part of the prosecutor’s case-in-chief.