Why what you say to the police can be used against you, but not in your favour?

Question

I'm asking this question from the viewpoint of an almost complete newbie in court law.

I've heard stated by plenty of lawyers that you should never talk to the police, and the only thing you should say is: "I want to talk to my lawyer". There are plenty of reasons given for this advice, one of them coming from the police itself when stating your Miranda warning: "[..] Anything you say can be used against you in court. [...]". It doesn't state that it can be used for or against you in court, but only against you. That seems... odd.

As a layman, I'd imagine that any type of evidence that is valid enough to be used against you, should be valid enough to be used in your favour. After some research, it seems that when the evidence is used against you, it is acceptable, but when used for you, it's considered hearsay. The definition of hearsay that I usually hear -- which is the one also present in the Wikipedia article -- is:

[...] testimony from a witness under oath who is reciting an out-of-court statement, content of which is being offered to prove the truth of the matter asserted.

Now, this definition seems to fit this type of evidence very well, so it makes sense that using it in your defense case would be invalid. On the other hand, that doesn't seem to stop it from being accepted in the prosecution's case.

So my question is: Why are statements made to the police considered acceptable as evidence when used in your prosecution, but hearsay when used in your defense?

Answer 1

This is a great question because it's a useful vehicle for understanding a cross-cutting principle of law: baselines and exceptions. I find that thinking of law as a system of baseline rules and exceptions to these rules is a great way to organize and make sense of the mess that is 'the law.'

A police officer testifying about what you told them, whether it helps you or hurts you, is hearsay. So, as you correctly pointed out, the baseline assumption is that that testimony can't come in.

But, the hearsay rule is famous for having a ton of exceptions to it. Two relevant exceptions here are: (1) statements against interest, and (2) prior inconsistent statements. If what you told the police officer was a direct admission of liability, or a statement that contradicts the theory of the case that you're presenting to the jury, either or both of these exceptions are going to kick in and make that hearsay admissible. These exceptions are not going to kick in, however, for hearsay statements that help you.

A humorous, but related, aside, is that there's some jurisdictional differences in how far the 'statements against interest' exception goes. In some jurisdictions it only applies to admissions of liability, but in other jurisdictions it also applies to simply embarrassing statements. My evidence professor illustrated this by, out of the blue, mind you, saying, in class, "I stopped wetting the bed when I got to college," and then explaining that in the latter type of jurisdiction, that statement would be admissible. He then paused after the class had finally stopped laughing and said "that's not true, by the way...I stopped in high school."

Answer 2

Why are statements made to the police considered acceptable as evidence when used in your prosecution, but hearsay when used in your defense?

They aren't necessarily considered acceptable. As pointed by Colin Losey, they are hearsay too and it would be an exception to accept them. This does not contradict the letter of the Miranda warning: they "can be used" — under certain circumstances.

Why what you say to the police can be used against you, but not in your favour?

It equally can be used in your favour: either you or your lawyer can use it at the trial, subject to the same hearsay exceptions.

Additionally, the police can decide to drop the case if what you say convinces them that they no longer have it.

Answer 3

Miranda warning is a warning given to you, in order to avoid you having legal disadvantages. It makes sense that they don’t have to warn you about advantages from making a statement. “If you supply a good alibi, you may be released without any charges”. That is true whether it’s in your Miranda warning or not.