My guess: the Witness is Dr. Elliot Jones, Katarina's ex. And Olivia is his and Jones's daughter Hannah, who Jones thinks is dead.
--Remember, Elliott CREATED the time machine. He of all the characters we've met, knows the most about time travel, more even than Jones. That makes him a prime candidate for being the Witness. He was even able to get Ramse a dose of the time-travel drug, way back in 2016 before the technology was fully developed.
--Peter Outerbridge's stature. He's a top-notch Canadian actor who has starred in numerous TV shows. Unlikely the showrunners brought someone so high-profile on for just a two-minute scene.
--Elliot's also linked to the red hallucinogenic herb which the Army and Jennifer use. Railly saw a whole room full of it in Raritan Laboratory; presumably this was created accidentally during Elliot's experiments, and he discovered its hallucinogenic properties later.
--Misdirection: He's super-deferential to Ramse in the scene where they appear together, bowing and scraping, so you don't think he could be the big bad. He's also depicted as an eccentric, geeky scientist, again, not the profile of the big bad.
--Olivia's references to her father are very negative. Elliot abandoned Jones when she got pregnant, so he's a lousy husband/father. Olivia said her father had plans for her; again, possibly meaning that Elliot had raised her to lead the Army. While speaking to the Witness in her vision, Olivia is angry and demands "What do you want from me?" If Elliot is the Witness and she's Hannah, then this scene makes sense.
--That Jones thinks Hannah's dead doesn't mean she actually is. Elliot could easily have brought her to another time and raised her without Jones's knowledge. Even if she'd had the plague, we know Col. Foster may have cured it.
From what I think I beleive it to be maybe Cole but not the Cole you see. It's pretty confusing but so is the series and the clutches of time in it. I think this is a Cole from a different reality/future.
One proof is that the Director of the series has stated that it'll be a plot twist on who the witness is and fans would feel as if it was obvious.
Another evidence to support this is it'll really be a blow if the witness is from any of the rest of the crew or even if it's a new character introduced.
The witness is a time traveller and therefore shouldn't be those who haven't taken a trip on the time machine
I don't think any of the primaries is one, Ramse's the traveller so he's not in. I guess we'll have to wait.
Je pense aussi que le Témoin est Elliot Jones car le récit n'en parle plus du tout après qu'il ait donné à Ramse l'accès à la machine. On peut penser qu'il la récupére et continue ses expériences.
Quant à Olivia/Hanna, l'idée me parait excellent car l'histoire ne montre à aucun moment sa maladie ni sa mort.
Serendipity - I love "12 Monkeys"
What if the Witness is actually Ramse's son? He showed Ramse about building a time machine and was thrown (time travelled) into a forest where someone was "waiting" for him Just like Ramse he was also taken from his loved ones and would think was cruel. He would have also seen stuff from the future and know of stories from the past.
Just speculation I guess.
James Cole is at the center of EVERY reference in every time period, including the "MAP' in the German Nazi scientists' place where the child version of the Messenger sent back to 1944 was kept in her room/cage. But that makes no sense, since the Nazi War criminal scientist was physically presumably by the 'witness' which led to his work with the child, and presumably the scientist would recognize him as the witness himself when they met. Or maybe the witness gave him red tea and took another form. Cole just doesn't look like the kind of guy who would even in his future concoct red tea and be able to possess people and be a wizard in effect. But he IS at the center of every thing shown so far.
Plus the witness is really a nutcase of the highest order, a veritable MeglaHitler with designs to destroy or control the entire Universe as it were. So someone either known or unknown has to possess a big enough ego to play God, and the evilness to destroy the world with disease and then destroy time itself. I don't see anyone alive on the show that fits that bill, even with the loss of their loved ones or not. That is perhaps the ultimate selfish act to destroy reality because your widdle heart is hurting and not think of anyone but yourself. but just speculation as has been noted, we may see lol
I am far enough into the series to know the identity of the Witness, but I a still unclear about his motivations,,,does he want to destroy everyting??
The Witness wants to destroy all of time and create a Red Forest, a place where time, and therefore death, does not exist.