Why should the police be required to advise suspects of their Fifth Amendment rights (to remain silent and to have an attorney present) when police are not required to advise people who consent to searches that they need not give consent?
Lawsuit / Dispute Attorney
Miranda v Arizona, a United States Supreme Court case, was the first decision to hold that if a defendant is interrogated following his or her arrest, any statements that are taken from him or her may not be used as evidence against him or her in any trial of the matter unless the interrogators first advise the defendant that he or she has certain rights. That bundle of rights are now commonly referred to as Miranda rights.
The reason these rights are given is to afford the constitutional protections of due process, especially the freedom against self incrimination.
The Fifth Amendment guarantees due process about all matters pertaining to laws of the federal government.
Our Fifth Amendment says.... "No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury, except in cases arising in the land or naval forces, or in the Militia, when in actual service in time of War or public danger; nor shall any person be subject for the same offence to be twice put in jeopardy of life or limb; nor shall be compelled in any criminal case to be a witness against himself, nor be deprived of life, liberty, or property, without due process of law; nor shall private property be taken for public use, without just compensation."
This has been interpreted by the Supreme Court as both a remedial requirement about other constitutional rights that a person enjoys that have been violated, and additional "procedural" and "substantive" components about how to restore those violated rights.
Public policy does not require that police tell people - prior to being in custody - what they should know by common sense, i.e. you do not need to consent to a search under any law anywhere in our country. Freedom from unreasonable government search and seizure is a fundamental and well know right ensured to all citizens by the Fourth Amendment.
You may find help in my Legal Guide "Constitutional Law: What is Due Process of Law?"
Check with a lawyer in your locale to discuss more of the details.
Good luck to you.
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Criminal Defense Attorney
The cynical, short answer is that most people in handcuffs at the police station will still talk while people who are on the side of the road and not under arrest will refuse to give consent even if advised of their rights. So judges are happy to give police officers cover to conduct searches and make arrests by keeping the public ill informed about their right to refuse consent to search, a breath test, or field sobriety tests.
A more serious answer would be that Miranda represented the Supreme Court's conclusion that the police were using intimidation and coercion to generate confessions and statements. They reasoned that where a person is in custody and being interrogated by the police, a suspect has the right to be informed of his or her rights, otherwise any statement made by that suspect is not admissible against them in their criminal case. Asking someone for consent to search is supposedly less coercive, but the courts have reasoned that because a person on the side of the road is not in custody, anything they agree to do is voluntary, so we shouldn't penalize the police by suppressing any evidence they obtain as a result of such a search. Having been asked to consent to a search by the cops, in my experience, this simply isn't true.
Disclaimer: This answer is provided as a public service and as a general response to a general question, it is not meant, and should not be relied upon as specific legal advice, nor does it create an attorney-client relationship.
Criminal Defense Attorney
I agree with the cogent and accurate assessments of my colleagues. Good luck.
This information is offered for informational purposes only, as I do not practice law in your State. It is not intended as legal advice and you should not rely upon it to decide how to resolve this issue. No Attorney-Client relationship is intended or established by this response. You are faced with a situation where you need to consult with an experienced defense lawyer admitted to practice law in your State before you make any decisions as to how to resolve this issue.