It's also true of statements made prior to custodial interrogation, it's just that the police don't have to read you your Miranda warning prior to taking you into custody.

This means that you have to be super careful when speaking to the police at all. And by super careful I meant: don't. Watch professor James Duane's videos on the topic, and Don't Talk to Police. Also, if arrested, you can't just stay quiet: since Salinas v. Texas the defendant must actually invoke their 5th amendment right to keep quiet before actually keeping quiet, otherwise their keeping quiet... can be used against them in a court of law. You'll learn that from watching professor Duane's videos.