It took me totally by surprise.
Which were the clues?

There were two points in the game where Ed would lower his head just before a fade to black scene transition that caught my attention. The kiss at the baseball field is one of them, but the first was at the end of the very first scene as Ed finishes the phonecall with Dr. Morales. It made me think Ed had black outs, perhaps from having multiple personalities, and it made me consider that 'unreliable narration' was going to become a big thing later in the story. I felt that the game was lingering on those two transitions to set up up a twist where these blind spots would be filled in.

Things turned out much less complicated than that, but I wasnt completely off mark. I still did not predict how tragic the reveal would turn out and I dont think anyone could have guessed what was going to happen even with all clues pointed out. Not until Ed took the gun, that is.

i had no clue Ed would turn like that , not till the moment anna closed the door with Ed outside , right then i knew she was not trusting him , but never expected the bullet to the head

I had a nagging feeling that there was something wrong with Ed and I didn't believe that the detective is traitor, but that's probably because I liked his character and being a traitor didn't really feel right. However the level of Ed's betrayal was bit of surprise for me. Anna was easily likable character and while some dislike her death, I thought it brought new level of drama to the game.

I have to add that I did find it weird why Ed was in same metro as Anna when I looked at the map and I thought that either it's an oversight or there's something fishy going on.

I suspected Ed most of the way as wanting the technology, but I had no idea he would go as far as he did.

I felt it so crazy that it sounds like a plot hole. If Ed was a non play-able character I can understand, but since you can ask all the character to describe each other it really seems that Ed become suddenly crazy. Besides it is completely unclear how to kill Anna could open the metal bars.

On the other hand he could be the only one... the cop has a too cool voice to be a traitor ;)

He should try some Trixopil.

There is another clue, I think: Ed's descriptions of the other characters when you have him look at them.

Compare, for example, Anna's opinion of Ed when you have her look at him: she talks about how she feels about him. It's been a little while since I played the game, so my memory of the thoughts given by others is rather faint, but I seem to recall that they follow a similar trend: they describe each other in terms of how they each feel about the others, describe them as people.

Ed, on the other hand--if I recall correctly--describes the others in terms of what they can do for him; perhaps most tellingly, when you have him look at Anna--who his actions seem to imply he might be falling for--he describes her as the means to getting to Dr. Morales' technology. Not as a pretty girl. Not as someone who he might have conflicted feelings about. Not as someone who he's concerned about. As a means to an end.

I'll confess that I didn't see the twist coming--I think that I held some degree of suspicion regarding Ed, but hadn't guessed that he would turn traitor--but I do think it rather well foreshadowed.

I figured it out when Bennett did. When Ray mentions that someone must have gone "out of his way" to frame Bennett, and Bennett finally realizes who it is.

Another clue - If you decrypt Morales' journal, there is an entry about how he doesn't trust Ed.
I missed this the first time.

I noticed the lowering of Ed's head after the kiss and wondered why he would do that, I eventually came to the conclusion that the had hoped for more than a kiss on the cheek? Well, no further distrust, that is for sure.

I have to say, I liked the story quite a lot until Ed became crazy. From this point on the game lost a lot of spirit and atmosphere for me... Anna's death was a mistake in my opinion. And the ending was disappointing, ultimately.

I just completed the game... No suspicion toward Ed, even if the cop's innocence was pretty obvious o me. But Ed ? No. Ray was much more shady (on his phone : "Goal : gain trust of the group").

A thing, Ed had no idea Ray read the one sentence of the letter that might have given him suspicion already, and that makes the effect of the last note a bit of a stretch. And he accepts to leave her alone in the room while Anna's choice is kinda predictibe ? That's a bit weak in retrospect.

But I really like the twist, and Anna's death. Most games get us used to the idea that playable characters can't die. Here the scipt doesn't follow the usual convention and that's nice - the betrayal without the murder woud have been much less dramatic.

I didn't trust Ed from the beginning, you see his place, so my first thought was he was a student at a university, also the tripod without the camera struck me. But then he's a well payed assistant.
Then there were so many things so off with him...
He was the one with the calculations of Resonance
He stalked Anna
His obsession with Resonance
The scene in which Anna kissed him
and litlle dialog thingys.

Then again, Ray wasn't to be trusted either for obvious reasons.
Bannet was also kind of the you-can't-be-sure-about-him type, not because of the note, but because he was on the one hand very light with regulations on the other very strict and didn't share much of his thoughts.
The only trustwothy character was Anna, though I didn't like her.

However I didn't suspect Ed to be the actual killer, I suspected he was going to betray the party at some point and that he was gonna do something to Anna was obvious from the dialogue, but that he was also the one behind the assault on Juno labs did indeed suprise me.

Also plantnig the evidence that he is a liar right in the player's hands from the start was a great move. Gave me that satisfiing feeling of getting sucessfully fooled by a mystery.

I never really suspected Ed because I don't like when main "point of view" characters hide crucial information to the reader/player and I tend to forget writers do it all the time. I was surprised Ed was my least favorite character (I usually have a soft spot for the nerdy type), but he struck me as arrogant and condescending. I guess I just assumed he lacked social skills.