Answered Is this common sense?

Of course, and if not I would definitely say it's a pretty good kill, especially not hearing any teleport sounds or seeing any teleport marks. Still hesitant though, I think someone might be able to get down the vents in 5-6 seconds. In fact, I have a video of me buying from the T menu and maneuvering down the vent in about 5-6 seconds.

(Player was slain/banned for loopholing/RDM for this one, BTW. Said he saw me with guass rifle in report, death scene showed otherwise) Shadowplay rocks.

 

Spoiler: Better picture of what happened

Sorry, I should've included this in the initial post to avoid confusion.

 

So they were still by the hole under the bed? Or they were by the hole next to the air lift (you know what I mean)?

 

I'm going to have to agree with Lightning with his two points on why it would be common sense.

 

In this instance, if there isn't any teleportation-residue, and there's only one player in the vent, it's common sense that he was the one who threw it.

He couldn't escape in time, as the grenade's duration is six seconds at the very most, which only results in him reaching half way to the nearest exit at the other side of the vent.

If there IS teleportation-residue, there is a chance that he made an escape with the aid of a teleport-er. You couldn't kill anyone in the vent as there is still a chance that they never witnessed the player "teleporting", which doesn't classify as G.B.A, which leads to suspicion. Unless you specifically saw them witnessing the player "teleporting", in which you probably already seen which player teleport-ed to begin with.