My group is restarting and it's become important for backstory how much or little knowledge of immortal elves exists. Will talk of immortality get blank stares, a shot to the face or a simple, 'heck if i know go read one of Eheans books, I think he's one'? Not just in the shadow community but also the world at large.

For general public it seems not a lot is known or confirmed if there are suspicions. After all they pretty much kept their heads (and ears) down through the centuries so yeah you could go to the Post and say Ehran's an Immortal and the editor would look at you funny saying 'That bookworm? Okay, if he is where has he been? What proof you got?'

Does the governments know more? Hard to say, plus it's easy to say Immortal but how do you prove it short of waiting them out... Plus I would think if the Corps/Governments were really sure they were immortal what sort of pressure are the elves applying to keep them from being treated like technomancers, aka chopped open and examined?

Just ask any Humanis Policlub member and you will get all the proof there is... and more... the immortal elves even sucked the life out from everyone they lay their eyes upon... like vampires and shit but in a whole different level. Even the Surge was their doing as they used the death of millions to get young again... etc, etc.
Does it answer your question?

It's been 60 years since the Awakening. Lots of Orks and Trolls have died of old age, but not any Dwarves or Elves yet. (Dwarves, mind you, certainly *look* old. Some are victims of early aging, where they look 40 at 20, but then keep looking that way onwards.) Science thinks that Elves will live a couple hundred years (Dwarves too!) but, as of yet, no one knows for sure. It's an urban legend, and sometimes names get tossed around, but there's no proof yet. How can there be? Check back in 200 years, we'll start finding out for sure.

And that is assuming they don't fake their own deaths and with a slight change of appearance reappear a few years later on the scene as a relative or totally new persona, like they have been doing for centuries already.

DNA makes that a little trickier but it wouldn't be much harder than removing a SIN etc etc.

Depends on the level of the testing.

If you were trying to pass yourself off as your own descendants, you probably would be tested to see if genetic code at specific locations along the chain matches against known samples of the lineage in question to confirm or deny you are of that bloodline. And seeing as you are the original bloodline you will pretty much test out positive.

It's pretty rare to have a full DNA sequencing done, especially for testing purposes, so it would have to be something fairly major to warrant someone being able to demand this.

The canon has it that Liam O'Connor status as a "spike baby" born in 1979 was publicly outed in 2015, when he took part in the negociations between the British and Irish governments and the IRA, that resulted in the Treaty of Galway and the reunification of Ireland.

Considering that the oldest "regular" elves born in 2011 were only 24 years old when Tir Tairngire was established in 2035, it is likely that a number of leadership positions were then filled with more experienced (and mature) spike babies. Some of the new nation leaders (Surehand, Ehran, Oakforest...) may have posed as spike babies then.

So even if people at large may not believe there are elves alive today who are several thousands years old, it should be commonly held that some of them are born before the Awakening, at least as early as 1979 and possibly before. By 2035, being told that someone was born in 1945 and still in good health would not stretch imagination a lot, since there would be humans in that case (albeit just not looking young). So people would just be left to wonder just how old could these elves be? Were they born in 1945? 1900? 1865? Before?

So at least conspiracy theories that Jenna ni'Fairra totally belonged to the Third Reich and Surehand was in Dallas on November 22nd, 1963, should be common.

as someone with some familiarity with the field, i can assure you whole genome sequencing is getting very cheap. it's not something that would be done to verify a sin, sure, but if you wanted to be sure someone was who they said they were it's not going to be prohibitively expensive, especially given the level of biotechnology known to exist in shadowrun. that said, there are probably ways to spike in enough DNA with variants in certain regions to look just enough different to plausibly qualify as a relative. not a serious issue if you can control the sample you give someone. if you can't you might have a problem.