Here's a case where a civilian is being arrested for driving under the influence of alcohol and endangering the lives of citizens, while also putting himself at risk. What are his rights? Is the cop obliged to read out the Miranda warning before placing him under arrest?
The answer is 'No'... And that's where comes the tricky issue of "your right to remain silent" as anything you say can be used against you in a court of law.
While the Miranda warning is mandatory under all other circumstances, it is not mandatory that the cop reads out your rights before making a DUI arrest.
That's probably because the defendant (innocent until proven guilty) is too drunk to understand the "nature" of his rights. So till he comes to his god-given senses -- or till he is assigned a lawyer -- he must try and remain silent.
For more on this, see
Protect Your Civil Rights - DUI, Miranda Warning and The American Law
