Would implementing a range limit be a cop out? Assuming pensieve reconstructs the memory of the donor around x meters of him works well. Then you can have mega pensieves as a plot device later for high range memory viewing.

 

My interpretation of pensieves is that all the information of the real event is there, but you need to know to look for it to see something the original host didn't. As in, if you're person C, viewing person A's memory, person B would be as if they're under a Notice Me Not charm unless you know (or have reason to believe) person B is there.

 

We can try to make range limit more organic. Not a fixed 2.7182 meters for example, but "how good was the memory extraction", "how much did donor remembers the memory" or "how much time passed since the events in memory". Soft limit works well and I see Dumbledore giving these three excuses in a fancy way.

 

I think the reason it was never used in court stems from the fact that Slughorn was able to edit his own memory, apparently temporarily, because he was able to produce the true memory later. I was under the impression memory charms were basically permanent, because they never fixed Lockhart, but maybe you can modify the mind-goop once it's out of your head. The False Memory charm seems to serve as the most likely explanation that Pensieves and Legilimency are not commonly used in court, if ever, and it quite possibly answers the original question. Slughorn was able to edit his memory, not reality, however much he would have liked to change the past. What Harry and Dumbledore saw was not reality, it has nothing to do with reality; both the false bit and the true bit came out of Slughorn's brain.
At the moment I have some idea there's no one else in the room with me because I can't hear anyone else and there isn't anything wrong with my ears. If I ever remember writing this stupid post, I could theoretically draw a third-person view of the room, and myself in it, out of a combination of earlier memories and imagination, though an advantage of the magical version of this process is that I would have a perfect view of all of those earlier memories, so I would know what the couch behind me has on it as I'm writing this.
I contend that Pensieve memories contain what you can extract from your own brain, whether you saw it, heard it, or made it up. When Hokey was sent from the room, her earlier memories were sufficient to keep the boxes in place until she returned with Riddle. Had Hepzibah moved one of the boxes for some reason, Harry would have seen a box appear in its new position. Had Hokey guessed that her mistress levitated it there, Harry might have even seen that take place. I realize that this model contradicts what was said in the interview, but we remember this is post-books Rowling and her supposition that the Pensieve would be only as useful as a diary is untrue. To recreate memories as clear and as detailed as they are in the Pensieve would be a bitch and a half to do, even if you recorded your life in Blender or Maya 2016 for some reason. Additionally, I'm pretty sure that if you were obliviated, you couldn't just extract your memory from your head, or they could have fixed Lockhart by just showing him his whole life.

 

I think the memory is limited to what the donor can know of the scene. What he could see/hear/smell if he paid attention, which is of course more than what he did notice at the time, but also what he can infer from his other memories.

For example, Snape's rendition of the grounds, the Marauders' faces and whatever isn't just what his peripheral vision notices, but takes into account what he knows they look like. Harry can still see the boxes, etc. after Hokey leaves the room because Hokey saw them before leaving, and has no reason to think they move (you'll notice Harry only describes immobile things during the time Hokey is out of the room).
That's my interpretation of the "It’s somewhere in your head" comment.

Now what about the things you cannot possibly notice? What happens behind you, or behind a wall, when the sounds and future events cannot give you an idea? I'm not sure, all logic say the one going into the Pensieve shouldn't see anything if the donor couldn't have an idea there was something to see, but it kinda contradicts JK's statement that "Pensieve memories are the truth".

So either in HP people have some sort of sixth (or seventh) sense that tells you what people are doing behind you from the feel of the air or whatever, or JK responded in the interview without thinking of the scope of her answer and you should only consider the latter part when she has a few seconds to think about it. In my headcanon, I use the second answer, but to clarify the canonical one, someone should ask her if you could use your own memory to identify some silent person who stabbed you in the back in a dark alley, or if the memory of a kidnapped child who's been kept blinded all the while would show the face of the kidnapper (assuming the kid doesn't know their voice, of course).

 

There is, indeed, an apparent contradiction from these two facts:

1. The magic of the pensieve shows wizards things they never saw and in fact could not have seen e.g. someone standing behind them, or words said out of earshot.

2. All information the pensieve shows comes from the mind of the memory-giver. (See for example Dumbledore in HBP stating that Harry should be pleased with the quality of his memory).

However, my sense is that JKR has some weird views about the mind which means, to her, there is no contradiction. Namely, that the mind is some kind of sponge which collects all information about its environment. Someone standing behind you? Doesn't matter, it's still in your head somewhere.

My personal preference in fanfic is to make memories quite malleable, and therefore unreliable as a source of knowledge. I dislike the idea of memories being used in e.g. law enforcement or trials, because it just seems to me to be too easy. Magic should solve the material problems Muggles have, but it shouldn't change the fundamental basis of human relationships or weaknesses in society.

The need to trust and the possibility of betrayal, the presence of doubt in the administration of justice and the possibility that you might be wrong, these are things that fundamentally magic should not be able to solve, because if it could then you remove interesting conflict from the wizarding world. A story where the protagonist can trust everyone and where miscarriages of justice never occur is dull.

 

I think it's possible to understand the Slug-tampering as a form of spontaneous magical repression, which is the result of the strong self-disgust that Slughorn feels. It is far more interesting to imagine that, on top of voluntary tampering, Pensieve memories are subject to all the psychological clusterfucks which our memories actually undergo: repression, obfuscation, lying to self, embellishment, self-affirmation, confirmatory bias, etc. Which makes them inherently unreliable, to the extent that they're completely useless in a trial situation (obviously, the same could be said to some extent about Veritaserum).
In fact, they're equally unreliable as diary material, but not more so than a written journal, which is subject to the same internal manipulation. However, contrary to the written journal, they don't require the conscious, dialectical effort of putting into writing one's experiences, which is a great vector of lucidity, facilitating enlightenened introspection over time. In this way Pensieves are potentially less successful as an instrument to self-knowledge than a journal. In my opinion someone like Dumbledore would have both, for the simple reason that Pensieves can show stuff which is indescribable. But it wouldn't replace a journal.
To the question of "range of memory" i.e. can you remember someone standing behind you. I'd say that a memory is a layered object (borrowing from Bergson), a construct that the mind returns to over time and "completes" over time: the memory of an event is not a finished object when that event ends. In that sense, there is certainly at least subconscious (or "deeper-conscious", as Bergson might say) work being done constantly, shifting our memories around, lighting them up with different emotion-colours, etc. When you extract it for viewing in a Pensieve, I gather the memory has been worked on by different psychological processes which have served to give it coherence and make if fit with what you know. If, for instance, something happened in your memory that could only have happened if someone had been standing behind you, but you hadn't actually seen the person, you might "fill in the blank", so to speak, though in a manner which might appear in a memory to be no less certain than what you are actually sure has occurred. Which again underlines the unreliability of the whole process, whereby aspects organically invented by psychological reworking for the plausibility/continuity of your memory become indistinguishable from the actual events.

 

One idea I like, although not sure if I've ever brought it up on DLP, is that Divination is not useless to those without The Sight.

Using Divination if you have the gift makes it very powerful, but even someone (with magic) who has no skill or knowledge would make a suitable medium, although they'd maybe need assistance to interpret it. On the other hand, a muggle doesn't have any magic to 'cast' the divination, so it would be like them attempting to make a potion, and lead to nothing.

Different forms of Divination would have different accuracy and precision. So going back to tea-leaves - they're accurate, in that they provide a view of the future/past; but not reliable, as they can display what's going to happen in truth, metaphor, or a confusing mix of the two. Harry finding the Grim in his leaves was thought to be an omen of death, not that he would literally encounter a black dog.

Pensieves work by using the memory as a target, or catalyst. It's not that you're viewing the memory, but that you're using the memory as the tea leaves to scry what happened. As such, they're accurate because the person who provided the memory would be able to direct the scrying to where was needed

But how precise they are depends on who provided the memory - if it comes from someone with a clear mind, who recalls the event in question easily, then there's a wide range to view before things get fuzzy. If, on the other hand, we ask Neville for his seventeenth breakfast at Hogwarts, we'd get a vague view of him sitting at the table, with a plate in front of him, and maybe be able to discern what he actually ate.

A memory that's been sabotaged wouldn't be able to 'target' the truth, so would be useless; and when someone remembers incorrectly, then the target is shifted, so the 'view' might be lesser - only able to see what was in their direct vision, rather than anything else.

This opens up iterative pensieving, where you can go back and look for further details, and use those to try and jog your memory better; but presumably if the details are wrong it can then throw things off further.

Also, this changes the whole thing from a 'memory recall item' into a diviantion medium, which is quite a bit different.