...let's move on to the demo.
For anyone who wants the source demo - this is the server's local version:
Demo
This
Demo is the demo immediately following where Trionkali gives Vinayill a chance to download the demo, then confirms that he has the demo, and then bans Vinayill.
There are a number of moments where Trionkali picks up on Vinayill's location, and all of them can be explained through line of sight, prediction, and use of sound. ac_desert3 is not a massive map, and there are several predictable pathways across it that any seasoned player will know how to take advantage of.
Watching the entire demo, particularly the engagements between Trionkali (Noun) and Vinayill (Guns'n'Nades), you can see Trionkali does quite well to pick up on Vinayill's positioning. Vinayill moves quite predictably, and takes the same direction out of the RVSF spawn nearly everytime he spawns. He also frequents pickups in his path regularly, which results in a lot of noise - making it easy to predict his location.
There is one moment where it seems quite impossible for Trionkali to know Vinayill's location, and that is at almost exactly 10 minutes remaining, where Trionkali is coming around a corner and fires at the wall near the direction where Vinayill is standing, having just picked up the ammo box there. Immediately following this encounter, Vinayill accuses Trionkali of wallcheating, in-game.
If you watch carefully in the demo, from the first person, it seems like the pickup sound occurs after Trionkali begins firing. This, of course, seems highly suspect. It is also the only moment in the game that seems like any kind of defining evidence that Trionkali is cheating.