Murderer Scenario

This scenario I made up has been bothering me for years and I want to know what others think of it. It will probably sound pointless to consider to most people, but this type of thing interests me.

Imagine that you're about to be murdered by someone (after being robbed or raped). He tells you that he needs to kill you so that you don't report him to the authorities, since you've seen his face and will be able to identify him. The only way he won't kill you is if 'promise' not to tell anyone about him. He then tells you that he's undergone training which has resulted in him having the ability to determine conclusively whether or not someone is lying from his/her facial expression (pretend you're 100% sure he can really do this to anyone). Do you think it would be possible to make the decision not to tell anyone?

The problem is, if you successfully tell him honestly that you aren't going to tell anyone, after he's gone, you're no longer threatened by him and have nothing keeping you from telling the authorities. But if you do tell the authorities at that point, you should have realized that you'd come to that decision back while you were being threatened, and therefore would have been lying when you told him you weren't going to tell anyone.

"the truth" changes, which is why the last bit of your scenario is a little paradoxical.
were I told to not tell anyone about the incident, after I had been robbed/had a gun to my head, I would have no plans of telling someone about the incident.
however, after the robber/brow-beater has left, I would call the police and ask to be given witness protection, or a similar protection.

without the laws we currently have for this sort of thing, the scenario would be all sorts of fascinating and intense.

if I were to put myself in the shoes of the murderer/robber, I would just kill the victim. there's nothing but risk involved in keeping them alive. I would have to be lost of all reasoning to leave them alive (or kill someone else at all, for that matter.)

How about switching the idea back on yourself? What would you be thinking about in such a situation? What's going through your mind?

Well, one obvious way to "sidestep" this problem would be if it simply didn't occur to you at that moment that once the criminal left, you might later feel differently about whether you should tell the police. So in that case you could truthfully tell the criminal that you don't intend to tell the police, but then still call the police later. But that solution is no fun! So let's assume that this couldn't or wouldn't happen.

So then it seems it would still be possible to make the decision not to tell anyone--you would just have to bite the the bullet and really decide not to tell the police. Further, this is probably the most rational decision. Since the criminal knows for certain from your facial expression what you will really do later, it doesn't really matter what you say, so you really only have a decision between two choices: tell the police or don't tell the police. If you tell the police, you will probably be murdered. If you don't you are more likely to live (remember that the criminal could always be lying, toying with you, etc.). So don't tell.

@No-Name
What would happen to me if I hadn't thought about the situation before is probably what DuB describes in his first paragraph. I'd genuinely decide not to tell anyone, but later I would. But since I have thought about it, I'd realize that later I'll have no reason not to tell anyone, so I couldn't genuinely say that I wouldn't tell anyone later, and would probably do what he says in his second paragraph.

@DuB
What you describe is pretty much what I've concluded about the issue. But it's still a very strange, counterintuitive decision that I think most people would have a problem accepting would be the rational one, because it would mean living for the rest of one's life doing something to avoid a threat that has already passed. It's almost like the cause comes after the effect.

It is strange, but mainly because we made the assumption that we would have perfect consistency and foresight (i.e., that we would realize at the time of the decision that later it would be beneficial for us to tell the police, and that our analysis of the situation would never change over time). We made these assumptions because they made the problem more philosophically interesting, but they're pretty psychologically implausible. As you say, in the real world it's more likely that even if we "truthfully" told the criminal that we wouldn't tell the police, later we would anyway.

If this happened after I got robbed it would be a non-issue. If you got robbed what is the worse case scenario, you lose a few hundred dollars? Your life is worth a lot more than that. I would make the promise then follow through with my promise and do what I said I would. That money is gone any way, even if you tell the police and they catch him, chances are you are not going to get that money back.

Many of the Liar's Paradox's are not paradox's at all, they simply involve a tense error, like you are trying to evoke.

There are a limited number of ways that one can violate the principle that predication is the inverse function of abstraction.

Could just say the guy has the ability to predict the future. So even if you truly mean it when you say it, if you end up doing it later he will know ahead of time.

Assuming an 'omniscient' criminal who will know if you ever change your mind and kill you instead of letting you go, then clearly the rational solution is to not tell anyone.

One of the ramifications is very odd though: once the criminal has let you go because you've decided not to tell, there is no reason not to tell the police, but you would be literally incapable of doing this.

Of course there is a reason not to tell the police, he can always kill you later. In fact that happens all the time in real life. If the person threatening is in a gang that has a lot of influence in the area or he is like a mobster or something, he tells you not to say anything or your going to die, and very often people wont tell the police because they are afraid for their lives.

I think I would end up getting killed because my mind works in a certain way and I'd instantly think this:
"I can say I wouldn't tell anyone honestly.... but later I would realise I could tell anyone what happened".
So that would show and I'd be fucked.