With respect to the Paladin's ability "Divine Sense" ability in 5th edition, would it be possible to argue that they could sense a Tiefling due to their infernal heritage? Both RAW and RAI points are desired, here.
I imagined that, considering they were Outsiders in 3.5e (the only other one I'm familiar with), they could be argued to be called Fiends…
BUT, as far as I can tell, they're classified as Humanoids. They're certainly not "native to the Lower Planes" like the Monster Manual says. They're just… humanoids that are infused with the essence of a Fiend.
I think it's hard to argue why their human (or whatever) heritage prevents their detection by a Paladin's Divine Sense. The best argument I can think of is that it isn't strong enough of a relation to get noticed, supernaturally. Is there a better argument present in the lore?