Miranda advisements are only required when the police are subjecting a suspect to 'custodial interrogation.' This means that you are in custody, essentially under arrest, and being questioned by the police.
When are you in custody?
Custody is defined when a reasonable person would not feel free to leave under a given set of circumstances. It is an objective standard meaning that it isn't that you, as an individual, felt that you couldn't leave. Rather, it is what the "reasonable person" would have felt in your shoes. In most DUI situations, this realistically occurs when the officer places a suspect in handcuffs BUT NOT ALWAYS. Your attorney should pursue this issue aggressively.
Whan are you interrogated?
Interrogation is when the police are questioning you and you provide answers. If you make voluntary statements such as "dude, I'm so drunk" without the police having asked a single question, that is not interrogation.
Again, your attorney should pursue this issue aggressively.
Expressed Consent advisement is different!
When asking you to submit to a chemical test of your blood or breath, officers are required to provide you with an "Expressed Consent" advisement. Essentially, they explain to you that you must submit to this testing or run the risk of losing your driver's license for one year or longer. A botched Expressed Consent advisement may have some positive implications for your Colorado DUI case.
Lack of a Miranda advisement is rarely a fatal flaw.
Most DUI prosecutions do not rest on statements made by the defendant. They usually are the product of physical observations of the arresting officer and the results of chemical testing of blood or breath.
Always consult with an experienced DUI defense attorney!
This issue is very complicated with numerous state and federal appellate cases to decipher. This guide should not take the place of a consultation with a licensed criminal defense attorney in your jurisdiction.