Alright, this might sound pretty convoluted, but I would truly value an expert eye to help me with a very theoretical situation.

I've been working on a science fiction novel where the whole world travels back a year in time. Before the time travel happens, a character (A) murders a famous person (B). The investigation is barely underway when everyone then alive return to their realities of one year ago.

This means that B is alive, but without any memory of the future or of his death. His old self is simply part of the reality the time travelers are brought back to. Could the criminal (A) still be found guilty of murder, intent to murder, or at least B's loss of his "future memories"? What approaches could the legal authorities take?

Any suggestions would be greatly appreciated!

  • $\begingroup$ In this situation, have they developed the ability to see into the future? In that jurisdiction, is determination by PreCrime of a future offense proof of a crime? Are the police onmiscient? Is this a Groundhog's Day loop, or does A eventually actually murder B without the world ending. There are too many unspecified plot variables to give an answer. $\endgroup$
    – user6726
    Oct 7, 2017 at 23:02
  • $\begingroup$ You're right, I haven't given enough info. Here comes: this is a Grounghog Day scenario but set over the same recurring year instead of day. The police is not omniscient, but everyone who was alive at the end of the first year remember what happened in that "lost future". The year will never be the same, despite some set facts like natural disasters and the like. $\endgroup$
    – MM Bolduc
    Oct 8, 2017 at 0:58
  • $\begingroup$ A's crime was investigated before the time travel and A is the prime suspect. Thanks for the quick comment! $\endgroup$
    – MM Bolduc
    Oct 8, 2017 at 1:10
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    $\begingroup$ The question might be appropriate in the World Building forum, but it is too far afield for law stack exchange. How a situation would be dealt with is largely a matter of opinion and depends too much on the details of how time travel is conceived in this scenario which has many versions (e.g. many world v. single time line versions). $\endgroup$
    – ohwilleke
    Oct 9, 2017 at 23:49
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    $\begingroup$ The question is asking about the actions of characters, so this does not belong here as it is too story-based. That being said... this event is literally without precedent, so you get to make up what happens. $\endgroup$
    – Azuaron
    Oct 19, 2017 at 13:46

5 Answers 5


There is nothing the authorities can do. There is no law which permits punishment for a crime which has not occurred. Even though the returnees have memories of the commission of a crime, such a crime has not yet occurred. And yes, the tenses get bent out of shape. The language has no experience with time travel, so it doesn't do well in this case.

B is demonstrably alive, so no murder has occurred. There is no law which protects the memories of a time traveler, so the destruction of such memories is not protected.

And in fact, since (it seems likely) the returnees have free will, there is no guarantee that many of their memories are valid. Oh sure, they can predict the weather for the next year with perfect accuracy (probably), but since they can act on their memories their behavior will almost certainly differ from what they remember. Certainly, B's friends and relatives will act to make sure that A does not have a chance to "repeat" his actions.

In classic SF terms, the personality transfers create an alternate timeline, one in which everyone has gained a year's worth of partly accurate memories. In this timeline, no crime of any sort has occurred, and none can be prosecuted. The law does not punish bad thoughts or intentions. The only exception I can think of is if A has begun negotiations with a hit man, in which case a conspiracy has been formed. This could be extremely difficult to prove, but a visit by the police to the hit man would stop that particular conspiracy in its tracks. A would then have to make new plans, taking into account the fact that his intentions are known for certain. This will complicate his task enormously, but he may consider it a challenge.


The answer really hangs on a point of law. It's actually a pity that law SE didn't decide to tackle this interesting hypothetical question.

Situation: A has murdered B. The crime has been investigated. Everybody will in the world is Groundhog Day'ed back one year. B is now alive, but effectively else knows he was murdered by A.

There are two possible approaches the legal authorities can take. One, they can warn for A from, again, murdering B or anybody else for that matter especially since they now know A is capable of murder. Two, they can charge A with conspiracy to commit murder. Conspiracy to commit a crime can be more heavily penalized than the actual crime itself.

Which course of action will be determined by the probability there is a strong enough case to commit A of the murder. For example, if the case against A was based solidly on forensic evidence then that would have been all lost when time reset itself to one year earlier. On the other hand, if it depended almost exclusively on witnesses who know what lead to the murder or who saw the murder itself, then it could be possible for the prosecution to take A to court on the charge of murder.


The Minority Report scenario

The scenario you have there is a variant of what we have in the film Minority Report. This scene touches upon the problem but does not go the full length with the argument.

Before we go into that, let us re-iterate some fundamentals of criminal law:

  • You can be sentenced for actions that you have committed
  • You can be sentenced for actions you were just about to commit, and only fortunate circumstances prevented you from going through with them
  • You can be sentenced for the action of preparing to commit a criminal action, although this is a lesser crime


  • You can not be sentenced if there never was any chance the action you were about to commit could have succeeded
  • You can not be sentenced for any actions you have not committed or attempted to commit

In the Minority Report case they dodge that whole problem of not being able to sentence people for things they have not yet done in that precognition happens so late that the law enforcement are always arriving in the nick of time; the crime is well underway and it is only by their intervention that the crime is stopped. So in Minority Report, they can sentence people for this: "we are sure that if it was not for us you would have gone through with it".( * )

Your case however is different. The murder is not even close to happening yet. Everyone besides (B)ob knows about it so they can whisk Bob away well ahead of time. And everyone can tell (A)lice "Hey, we know... do not be trying any funny stuff now!".

Then again... Alice has already gone through with the action. Alice actually did it. The fact that the damage has been undone should not matter. The action has been performed, so it should be actionable.

Then, yet again: where is the proof? Bob is alive, so there is no dead body. There are no forensics. There is no evidence. And even if the entire world knows that — yes — we have had a magic time-travel event( ** ), all they have to convict Alice on is the sworn testimony of those that started the investigation. And Alice can lawyer the living daylight out of the prosecution:

  • "Nope, was not me, you cannot prove it was me"
  • "Ok, so I did it but it was self-defense"
  • "Fine, it was not self-defense but you still cannot call it murder, it was manslaughter or an accident.
  • "Bah... it was no accident but I was mentally incompetent at the time due to depression/schizophrenia/being extremely upset because Bob did something really nasty to me and mine. I am fine again thanks to the magic time-travel event."

There is no way to get a case that will stick to Alice, hence they cannot possibly convict her.

So in the end...

...it probably turns into one big "Meh...". Alice is released by the authorities with an annoyed grumble, a warning finger pointed in Alice's face saying "Don't even think about doing it again!", and a huge sigh of relief that Bob is OK.

( * ) SPOILER: And then there are some other flaws in the system, but those are a separate issue.

( ** ) Or have we really? Maybe someone just screwed with our memories and implanted false memories of a potential future?

  • 1
    $\begingroup$ I believe that it is actually more close to Minority Report than to Minority Report. In Minority Report precognition could happen days in advance and they actually could sentence people based on that. (Forgive me my little play with links please ;) ) $\endgroup$
    – Mołot
    Oct 19, 2017 at 12:37
  • $\begingroup$ @Mołot Well I think it still differs enough. In the TMR scenario, the law has had time to prepare for this and make the necessary changes. In OP's scenario, we have present law, and present principles.... they have not been able to adapt to this magic event. $\endgroup$
    – MichaelK
    Oct 19, 2017 at 12:43

I would say that in this occasion the laws might have to be bent, as this scenario is completely unpredictable. A should be charged with attempted murder, because it was undone and therefore not actually murder. Some would be in favor of bending the laws to charge murder, but some would try to keep the law rigid. Tons of scenarios. The decision ultimately falls to the characters, more specifically whichever mass wins a debate.

  • $\begingroup$ A great thanks to all of those who have commented! This is a lot of food for thought and I will do my best to do it justice in my writing! $\endgroup$
    – MM Bolduc
    Oct 11, 2017 at 23:22

My best guess is that it could depend on the nature of the murder. If it was premeditated then there could potentially be grounds for conviction.

I think a possible argument someone could use against convicting this person would be double jeopardy, where you cannot be tried twice for the same crime. Criminal A may be convicted under a lesser included offense. Instead of a murder conviction, they may be convicted of attempted voluntary manslaughter. That may only work if it was a heat of the moment thing though. I could be way off, so let me know if I'm misinterpreting the Wikipedia pages or anything.




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