Cheat or not to cheat this is the question

How do you define cheating? This is a very gray area... Technically, using a third party tracker is cheating, yet a lot of people do it. Is using a web map that gives you a location of pokemons (like vegas pokemap) cheating? How do you prove it?

Location of caught pokemons is hard to use because a lot of people travel (e.g., I've caught pokemons in Boston, New York, Stamford, Chicago, Philadelphia, Montreal, Vancouver, Russia, Iceland, Sweden, Denmark, etc.).

Having a lot of a certain pokemon is also misleading - highly dependent on how much you play and where you play.

All in all, I don't think that there is a reliable source of finding cheaters by just looking at the app. I think you'd have to track distance / time-to-gym takeovers. But even then, really hard to discern who is actually driving from gym to gym vs .spoofing. The only thing Niantic may be able to reliably track are "teleporters" - people who travel ridiculous distances in no time. But even that may be unreliable and cheaters will smarten up to it.

Wish I had a better answer for you.

What for? That's is my question!

Well, the first I would look in the app that can be suspicious of cheating are the mons themselves of course, if you see a full page of 3300+ Dragonites, he/she is a cheater. Look at their Dratini candies, the dust they have, then look at their medals, search for the 2 more difficult ones, Dragon and Ice type medals, if you see insane amounts there probably he/she are cheating.

Pokédex is not enough even if you see a regional out of their place, people can travel of course. But for example if you are in Europe and see a lot of mon on their box from Santa Monica or NYC that are two of the best places to hunt probably in the world then you can suspect and a LOT that he/she is a cheater.

Another posible indicator, their starting date, if you see an account level 35+ with a lot of ultra rare and high level mon and only playing since 2 months ago, you can also make your suspects, even that guy has spend thousands and thousands bucks on eggs (check egg medal too) or he/she is cheating.

Other kind of cheating like spoofing to take down gyms and using maps are almost imposible to find, but normally people that do that will have a lot of rare mon as I said before, so you can probably cacth them that way.

It's very subjective. There's no way to know for sure, but you can come to logical conclusions based on...statistical anomalies.

What I mean by this are % of rare / ultra-rare Pokemon at 98-100% IV.

Take this one guy by me for example. I've seen him seemingly everywhere by me. Check gymhuntr, and he has defenders over a 20 mile area (in a city with a TON of gyms). That by itself is nothing - I have Pokemon in all the same areas - a couple stragglers that are still holding on in lvl 10 gyms.

But this guy....let's just say in ONE park....in maybe one square mile has FIVE Maxed 100% IV Dragonites.

I mean.....I forget the exact odds, but it's something like 1/200 hatches are 100% IV, and 1/2,000 spawns. So either this guy caught over 10,000 Dratini, hatched over 1,000 Dratini, he's the luckiest human being on the planet, or he's cheating.

There's another guy by me just like that with lvl 30 100% IV Snorlaxes. I haven't seen a Snorlax in 4 months. This guy has about 7 at 100% IV.