The burden of proof rests on the prosecution. If we require a statement, the burden is either partly shifted to the defendant (not the defense, just the accused), or the threat of perjury is now very real. While typically not prosecuted, a reasonably solid case plus threats of additional charges like perjury and obstruction of justice make it easier, and more affordable, to plead guilty or no contest.
(btw parent - torture is explicitly off the table, as apparently its no big deal to society if a confession is tortured out of someone because they can always come back and get justice, in every case, without fail, so your comment is irrelevant. instead you should have gone with "any coercion other than what is not legally considered torture nor duress" which I think OP has some other weasel requirements to invalidate but can't be arsed to figure out which)
You (OP) have to consider this within the structure of the justice system, and all of its leanings toward potential abuse. As a defendant, with little or no power, a lengthy appeal process, and if vindicated a lengthy and expensive road to exposing abuses, you are automatically at a disadvantage even if you don't self-incriminate.
Scenario: I talk with the police, or prosecutors. At any point in the future, I mis-remember or mis-state something, on the record. Immediately anyone can say we have evidence that you are at best unreliable and more likely lying. Nothing I say at that point holds any water. I have damaged my own case, and it would be far better had I not said anything if it were optional.
In this example, we can consider the types of evidence that lead to Innocence Project victories because DNA evidence proves that the evidence was really just circumstantial. This isn't just clearly circumstantial evidence, which cannot be used as the sole evidence in a criminal case. This is the kind of rock-solid, 5 eye witnesses, your vehicle leaving the crime scene, you are guilty of murder evidence. But you didn't do it, and you are set free after years in jail.
Let me interrupt you and say that Innocence Project victories are not the subject here, they are only proof that people get convicted of Very Serious Things (c) on very shaky evidence, so don't claim that this type of scenario is impossible.
Instead of mis-stating, I can remember more details which are relevant, and share those when I have to. Either I was hiding them originally, or I'm making them up now. I am undermined, and two eye witnesses who claim it was me now outweigh me, an obviously guilty person lying to stay free.
False memories are surprisingly easy to create, especially accidentally. Depending on the timing and nature of the questions, you could develop a false memory. Your statements will be different because you remember what happened differently. Better to write down what you remember and put it in a locked, unpredictable location.
Any number of variations on scenarios like this boil down to one thing: the moment you appear to contradict yourself, your ability to defend yourself is diminished.
Very clearly, "frequent contributor Bennett Haselton" has never been in a situation with another person where he/she had to say "that's not what I meant." And even more clearly, has not uttered the words "that's not what I meant and you know it." I'm going off into the gender stereotypes here, but I'm fairly certain that everyone over the age of 15 has met that one super-bitch who decides what your words mean, and can recite everything you have ever said when it best suits her argument. Even if that super-bitch is a dude. When the police or prosecution have a record of your statements, "that's not what I meant" works never.
"It is better that ten guilty persons escape than that one innocent suffer."
That's all there is to it, really. But I'll ramble more.
I'm having an affair, and my lover is the only alibi I have, along with hotel receipts and probably security video placing me anywhere but the crime scene. Were I allowed to take the fifth, I make the prosecution find more evidence and hopefully find the actual criminal, without exposing myself any more than I already have. If I share my dirty little secret, that leverage can lead to pressure to allow more invasive searches or questioning. If I instead make up another place and claim I was there, that's lying and obstruction even if I clear things up later. All of which can be used in the event they decide I'm the only suspect and proceed. Just hand over the paper trail, it's all a misunderstanding, and everyone laughs, right? No, your question was the benefit to society as a whole. Like it or not, married people will have affairs as long as single people, or other married people, are willing to be the mistress/poolboy, so there is no net benefit in outing a frowned upon but natural behavior. And dragging the innocent through a legal quagmire is hardly helpful in catching the real bad dude.
What if 10 of my friends say I was at the lake, but I say I was at the hotel, and my girlfriend (who obviously will just say whatever I tell her to say) is my only record because I paid in cash and avoided all but the most grainy video surveillance? I have no paper trail for the lake either because that was my cover story. Now I'm looking like the number one suspect. I can't imagine any world in which there is benefit to society in trapping me in my own web of lies which are completely unrelated to the crime, while the actual criminal is out there.
Now, you shouldn't have to answer questions that are none of anyone else's business; if your alibi for the night of the murder is that you were at a somewhere you're embarrassed to mention, you should be allowed to say, "I didn't commit the murder, but I would prefer not to tell you where I was." But Fifth Amendment absolutists would say that you don't even have to answer the question of whether you committed the murder at all. That, to me, seems absurd. Isn't society entitled to know whether you committed the murder or not?
Yes, society is entitled to know. Is society going to believe me when I say no? The answer is no. Society gains nothing by me answering yes, because that is a false confession. Society gains nothing by me answering no, because society doesn't just take my word for it and move on. Separate from railroading and abuse, when a prosecutor has a good suspect it doesn't matter if you are innocent or guilty - only whether prosecution can meet the bar to get you convicted. No corruption, no railroading, just well-intentioned people on all sides going with what seems to be the obvious answer. I'm guilty, and lying about it.
If you consider the benefit if someone is actually guilty, it is hard to come up with a good scenario. But guilty is decided after the presentation of all evidence, not when you have the chance to decline answering questions. And guilty is not the record of what actually happened, it is the decision of a judge or jury based on evidence presented, which becomes a legal fact, possibly altering history if you are legally guilty of something you did not do. Unless you assert that you can tell when a person has been correctly imprisoned every time, there is no way to work your way back and say we would have let a guilty murderer go if not for his self-incrimination, therefore the benefit to society is obvious. Because after 10 years in jail, he too could be an Innocence Project victory, and your argument shrivels into the pointless mental masturbation that it truly is.
Christ on a cracker, I can't believe I wasted that much space on stating the obvious.