Most people do not understand warnings given to them by police officers. Let's look at the Miranda warnings in the US. A standard version of them is something like this:
You have the right to remain silent. Anything you say or do can and will be held against you in a court of law. You have the right to speak to an attorney. If you cannot afford an attorney, one will be appointed for you. Do you understand these rights as they have been read to you?
If you look at it closely, you'll see it only applies to anything that the suspect says. In point of fact, a suspect has quite a few other Constitutional rights, that there is no requirement that the police mention. (However, failure to follow them can come back and bite them in the ass.)
In the US, if the police don't question you, then Miranda does not apply and they don't have to give you a Miranda warning. Here's an example. Suspect is stopped doing 80 mph in a 70 on the interstate. Officer asks driver for license and registration, then asks driver to leave car. No questioning and no need for Miranda rights. Officer asks suspect if he can search car. Although a question, it's not a question covered by Miranda, so Miranda still doesn't apply.
However, you have a Constitutional right not to be searched. But the police officer has no legal requirement to mention that little fact to you. Suspect agrees to have car searched and officer finds a gun. If officer asks about the gun, then Miranda warnings should be given beforehand. If officer doesn't bother to ask suspect about the gun (officer has already found out suspect is a convicted felon) and does a cuff and stuff, then there's still no reason to give the suspect their Miranda rights.
The English caution is roughly similar to the US, although there is a major change.
You do not have to say anything unless you wish to do so, but I must warn you that if you fail to mention any fact which you rely on in your defence in court, your failure to take this opportunity to mention it may be treated in court as supporting any relevant evidence against you. If you do wish to say anything, what you say may be given in evidence.
In England, if a suspect doesn't say something at arrest, the jury can draw inferences from that fact when the suspect subsequently testifies about it at trial. And in England, unless the suspect is questioned, a caution is not required.
Canada, on the other hand, has a different approach. It's warning runs like this:
You are under arrest for _________ (charge), do you understand? You have the right to retain and instruct counsel without delay. We will provide you with a toll-free telephone lawyer referral service, if you do not have your own lawyer. Anything you say can be used in court as evidence. Do you understand? Would you like to speak to a lawyer?
Notice how it doesn't apply only to what a suspect says, but pertains more to the fact that a suspect has the right to an attorney (which is the same as the US, but the police don't have to inform you of that fact). In Canada, everybody is required to receive the warning.
Other countries have different versions of notification upon arrest.
I don't know how many clients hoped their cases would be thrown out because the police "forgot" to give them their Miranda rights. But because the police didn't question them, Miranda didn't apply and their hopes disappeared almost as fast as they expressed the hope to me.
Best of luck,
Jim Clark-Dawe