Any thoughts on this are very welcome!

Hi,
Does anyone know if there's a word or phrase to describe a situation where someone is trying to argue that something must be true or accurate at a singular, earlier point in time because it went on to happen at a later point in time thus justifying their argument in their mind that they were right to think it was true at the earlier time point?

Possibly some type of logical fallacy? Or psychological phenomena? I'm trying to make a point about such logic being erroneous, it's really important, and I'm sure there is something that describes such situations but I can't remember!

I keep thinking of self-fulfilling prophecies but that's not quite right I think, especially in circumstances where what's being alleged isn't true but people think it is.

Bad hypothetical example to illustrate and not the situation I'm trying to rebut :

say someone was to say that another person was a murderer and then later that person went on to be convicted of murder either rightly or wrongly, wrongly is more analogous with the actual situation I'm thinking of though, in my mind this doesn't make it true that the person was a murderer at the earlier time point and indeed, the conviction could have been influenced by the jury hearing that other people have believed that this person has been thought to be a murderer in the past because of the person who previously alleged this.

Any thoughts on this are very welcome!

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