I think the issue of Tom Riddle's magic not being detected when he killed his family is not so much of an issue, because we know already that the Ministry ignores the Trace in areas where magic is normally used by adults i.e. magical households and their surroundings. The Gaunt residence was one such magical household.

So all that is required for Tom Riddle to evade suspicion is for the "ignore Trace results in magical areas" process to be automatic rather than manual (because if it was manual the person tasked with filtering the results would see that it was a killing curse).

 

That's...almost exactly what I said

That was the whole point of my algorithm, that the Trace spell(s) only reports identifiable spells that don't occur in a Wizarding location or in proximity to an adult wizard. So Tom Riddle casting a spell close to the Gaunt shack and/or close to Morfin Gaunt('s wand?) wouldn't be reported at all. And Harry repelling Vernon doesn't show up on Umbridge's radar because it's not an identifiable spell, just a burst of accidental magic. (And wouldn't she have *loved* to put him away for using magic on a Muggle...)

Which raises questions like, does the Trace work in Unplottable locations? Does the Trace register underage magic performed in a Fideliused location? Performed by Fideliused people? If Peter hadn't ratted out the Potters, could Voldemort have eventually found them by Tracing (?) Harry? And how the hell do owls even find people

 

It's not exactly the same. I'm not saying the magic ignores the result, I'm saying the Ministry bureaucracy ignores it. I don't think magic works in an algorthmic way, and even if it did, I don't think it would be the algorithm you suggested:

The problem is the bolded part. If it was possible to detect all magic in the UK, then surely the Ministry would be using that power and not imposing limits on itself. That would massively aid the detection of dark wizards and other illegal activity.

It seems clear to me that the Ministry is limited to the Trace in terms of detection ability.

Furthermore, your algorithm directly contradicts canon, in that we know that the Trace is applied to individuals, so it is not possible that it crawls the entirety of Britain. It is essentially a series of aggregated local magics rather than a single massive spell.

Finally, all this is merely an extension of what I said in post #26 in this thread about the difference between detection and illegality. I'm saying that the Ministry could well have detected Tom Riddle's magic but deemed it legal. The stuff about the wands could have been Tom Riddle covering his tracks for when they investigated the murders.

 

See, this is the part that stumps me. Because it would require the Ministry to be incompetent to the point of abject stupidity to deem 3 Avada Kedavra's cast in quick succession legal. If we're taking at face value that the Trace is cast on individuals and not wands, locations or entire populations, the department would've been notified immediately the spells were cast that they were Avada Kedavras cast by Tom Riddle Jr. Yet we're not given any indication that they even knew he was ever there, to talk of the almost immediate owling that Harry received after Dobby's Hover Charm.

 

Which is why I said it was an automatic bureaucratic process when they ignore the Trace in areas known to contain adult wizards.

No. The Trace is cast on individuals but cannot determine who has cast a spell, only that it was cast in that person's vicinity.

 

I can't remember, but I think I read a theory by Taure once, where he offered a situation that would be a perfect solution to the three killing curses contradiction here.

In fact, there are several, allowing for canon-compliance and removing the contradiction:

1. Tom killed them via Morfin under the Imperius Curse. (Taure makes too many posts for me to comb through them looking for his explanation, but it had this a suggested posibility)

It allows an Imperius spell to be ignored, and in addition, the killing curses were performed by a fully grown wizard.

2. Alternatively, Riddle took Morfin together, under the very same Imperius, and was the one doing the killing.


3. A third version simply says that the Gaunt's shack was close enough to the Riddle manor for the location to be the same in the ministry papers. Perhaps it's just not as exact as they want it to be? Or, they allow for leeway of wandering local wizards, assuming that all spells in the are come from them - as they are not directly monitored.

 

How do we know this?


Quotes from the chapter follow, emphasis mine:

It's only an educated guess (although Dumbledore makes good guesses) that Morfin wasn't there.

All we know for sure, his wand was used, and he woke up with different set of memories.

Also, 'over the way' is at the other side of the street, although there's mention of 'across the valley' which makes it a bit uncertain. I'd say that wizard's residence includes a bit of leeway to the distance you're able to cast spells without alarms going off, but that's again, an educated guess at best, and alas, I am not Dumbledore.


EDIT: 4. Perhaps, the presence of the "other wizard" is simply, a presence of a wand that doesn't belong to an underage wizard.* And the ministry puts an note (Morfin must have been nearby) on the file, and puts it into a a bottomless filing cabinet no one ever opens.

*If that is true, Harry did Neville a disservice by making him good enough to be bought a new wand. Removing a possible loophole for an Indy!Neville to use.

 

Version 1 was mine, in post 21 of this thread:

 

Yes, this, very much so.
wordhammer sorry for miss-remembering and comparing you to Taure.

 

Well how was the Ministry aware of Dobby's magic in CoS? Unlike OotP, when you can make the argument that Umbridge was keeping tabs on Harry herself, there's no indication that they particularly cared about his existence then. Not to mention Dobby was sure his own act of magic would get Harry expelled, so he must have been aware that the Ministry would be notified of any magic around an underage wizard.

Of course Rowling could have retroactively crafted the Trace around those incidents, but you'd think she'd pay more attention to the recently-written triple murder than to the hover charm from years before when making sure things fit.

If a writer insists on leaving logical flaws all over her work then welp. Death of the Author and all that.