If there was any that remained after all the rezes and heals, it should have DEFINITELY been removed from him at close of S8 where he speaks about the trials "purifying" him. I mean if that didn't get rid of the demon blood, then there's no meaning to the word "purify" any more.

Also in S9, seems like having Gadreel inside him would have purified what was left as it seems unlikely for any non-Lucifer angel to be able to occupy a demon blood infected body.

ONLY possible exception is that when Crowley went into Sam to get Gadreel out, he reinfected the boy.

Sam only believes the trials were purifying him. He had no evidence. He may of been so desperate and so unused to the strange energy in him he believed it. What I believe from what I've seen the energy was just burning him up, using him to build before being released at the end of the 3rd trial to close the gates.

Saying he was purified during that I think is poor writing. Pretty big deal this demon blood business is and if he is going to be cured it should be a big deal not some one liner.

I don't believe for a minute angels who posses humans with demon blood can possibly remove it. Nobody mentioned it for starters. Demon blood isn't a disease, its a different kind of species blood isn't it? Oh and if they could cure it I'm sure demons would be curable. Again I think its also poor writing to have angels be able to cure it.

Just like before he has it. Its latent again and causing no problems because Sam hasn't gone darkside like Ava and Jake. But he was soulless you say. Well he never felt anything so he couldn't of felt any pull to the darkness. I'm pretty sure the writers didn't want to bring it back there as it would of changed a lot of that early season.

I thought that it was stated on the show that a demon was a human soul that had been twisted by torture (in Hell). Lucifer made the first demons (starting, supposedly, with Cain). This was early stuff, like season 3, maybe even earlier. I don't remember whether it came up when Meg possessed Sam, or when Dean had the vision that he would become a demon. That was "Yellow Fever," I think. Or the episode when Dean was trapped in a basement with the girl demon. Cain and Demon Dean would be the exceptions to the souls being twisted by torture in Hell.

The offspring of a human and an angel was a Nephilim, which was the girl that Castiel and Metatron killed when Castiel thought he was completing the angel trials.
The offspring of a demon and a human was the anti-Christ child, the one with the powers to make things happen just by thinking them.

I accepted that the trials had at least begun the process of purifying the demon blood from Sam. Sam offered his confession in "Sacrifice" to be pure so his blood could be used to cure Crowley.

Ok, knocking out some misconceptions all at once.

But Cas wasn't an angel. He was human. So yes Hael still needed permission.

No, Cas was mortal because he didn't have his grace. He was no more "human" than you would be a snake if your arms & legs were cut off. Yes on the superficial level ya'll have some commonalities (no limbs for example) but the essence, the core of what you are doesn't change. Likewise, Cas didn't suddenly grow a soul or become a ghost upon death when he had his grace removed. He was still an angel, just a depowered one.

No, this isn't correct.. it was confirmed in season 3 that a demon was a human soul corrupted by years and years of torture in hell. The human was bad enough to go to hell in the first place and then their souls are corrupted. Humans and demons have a connection, humans and angels and demons and angels do not.

Demons and humans share a connection. Humans and angels don't and neither do demons and angels.

You completely misunderstand.

1) Season 3 was also during the show period where it was an absolute rule of Kripke that angels did not exist.

Supernatural, Official Season 4 companion, page 8:

Yet they [angels] almost never made it onto the show. In the first three seasons, Kripke had a staunch "no angel policy." Supervising producer Sera Gamble posited the idea of angels back in season two, with her episode 'houses of the holy', "but the reason [the creature] didn't turn out to be an angel in that episode," Kripke relates, "was because at the time I had the no angel rule - I just didn't want them.

2) I didn't say humans & angels shared a connection, I said demons were a MIX of angels & humans.

Supernatural, Official Season 4 companion, page 24:

Eric Kripke: . . . "Demons and angels actually have more in common with each other than they do with humanity, so they play by the same rules in a way."

Co-executive producer Ben Edlund elaborates. "The existence of non-corporeal entities possessing from both the demonic stripe and the angelic stripe indicates an underlying physical world that we don't know about, which is consistent with the supernatural physics of our universe. Lucifer, who was an angel, goes to Lilith, and using some of his angelic powers, which comes from God, he twists her into a demon, so it's like using good for bad. Demons are linked to humanity, but they are different, and their difference comes from angelic intervention, so ultimately demons are a bit of a fusion between human stuff and angel stuff, therefore it makes sense to me that their ability to possess, their ability to become non-corporeal, and all the other things that are not normally the province of humanity actually stems from the angelic perversion that came from Lucifer."

That's funny because I just watched First Born and Cas told Sam as he was trying to extract the grace that "being human taught him to appreciate human life". So was he merely mortal or was he human.

Unfortunately all we mere average viewers can go by is what is shown on our TV and the dialog provided. Just because interviews and companion articles may have stated some opinions from Kripke and Edlund doesn't make it canon. I think we have to go by what was shown. So since it was established that demon/human crosses created an anti-Christ and human/angel create a nephilim that is what we have to go by. Never was it ever stated on the show that demons were a human/angel hybrid.

WOW Thanks everyone this Throw Out line by Jared has created really great discussion THANK YOU We all feel that Sam is pure - some of the twitter responses thought that Sam was confusing Purification with Dying - They believed the trials where killing him not clensing Sam.

For a person to be cured of a blood decease they need blood transfusions ? Sam has not had blood transfusions - his blood was blessed for the trials.
But as one fan said we can only go on the story that is written and the dialogue given Has been a interesting Chat though Thanks Jenny

Maybe Jared and the writers were tossing a idea around because of these visions Sam is going to have next season

And I have to agree with Cheryl. The scene where the purifying was brought up in the first place was
beautiful,

Just to get this out because I don't like being misunderstood. I wasn't saying the church scene in Sacrifice
was bad! Just the fact they slapped on the purifying thing on like it was a last minute thing. Demon blood was such
a big deal it was a main and consistent (ish) thing in a season.

what was a crime though was that they put the possibility of Sam not having demon blood any more out there
and just dropped it, unresolved. Sam's demon blood is a core issue on the show since the beginning. To bring it up
and then dump it is a major issue for me. It needs to be resolved one way or another and given it's due. Now that
Sam seems to be experiencing "visions" of a sort again,

Exactly what I was thinking. Couldn't of put it better myself.

it could be that he still has demon blood in him or grace in him or both. I'd love to see both of those
dropped plot lines receive some attention.Imagine if demon blood, angel grace and human blood made a new
being..

Ah... well you may think I'm weird but I had a dream about this, though only if a demon blood and angel grace combined. And yes it was Sam

The offspring of a demon and a human was the anti-Christ child, the one with the powers to make things
happen just by thinking them.

Don't get me started on the anti christ plot. Although I thought Lucifer gave him the powers?

WOW Thanks everyone this Throw Out line by Jared has created really great discussion THANK YOU We all feel that Sam is pure - some of the twitter responses thought that Sam was confusing Purification with Dying - They believed the trials where killing him not clensing Sam.

We do? I disagreed. I strongly believe Sam is still unpure. I believe the purification and dying were mutually exclusive. Purification by death.

Maybe Jared and the writers were tossing a idea around because of these visions Sam is going to have next season

I just want my badass Sam from Yellow Fever back.

I think that the return to the demon blood in Sam will turn the show into self-parody. But I see the possibility of a conflict between brothers about it, and it will be much more convincing that "not looking for" or the "better brother".

I'm afraid I was not clear enough. I think that Sam's blood purification issue can be dealt more clearly, but I think that it will be a very unfortunate idea if after season 8 it will turn out that Sam still has residues of demon blood and if the writers tie his visions with demon blood again it will look circular and out of any fresh ideas. But, if they return to the idea which was put aside in season 2 that Sam's extrasensory abilities are inborn and not connected to demon blood (remember the next generation of children Azazel was looking for? It was implied that he was looking for children with abilities to feed them his blood, not vice versa. And Missoury, she said that he was extremely talented) that may be more interesting. Especially if we see that Sam is sure his visions are not connected with demon blood, because he doesn't have any, but Dean is not so sure and is terrified of the possibility that such connection may exist. And eventually if it comes to the issue of trust to his brother, then it may lead to some evolution in their relations, not running the same vicious circle again and again: I trust you/I don't trust you/I trust you/ I can't trust anybody right now/I'm with you 100%/I don't trust your desiosion and so on, and so on. It's tiresome for a viewer if they are not a hardcore fan, you konow

Sam still has residues of demon blood and if the writers tie his visions with demon blood again it will look circular and out of any fresh ideas.

Curious, I googled "SPN Sam has visions again" knowing it was likely a spoiler. Wow! Finally something is happening to Sam that isn't standing in the background being worried! Normally I don't like spoilers but its such a relief to see Sam getting attention. *zips mouth* That's enough from me. I don't wish to spoil anyone still trying to avoid spoilers.

Yeah, especially he is much more interesting and fascinating character, may be it is because of the lack of his POV, but that's the case. I don't quite grasp the reason of putting him to the background to reveal what exactly? Dean's dark side? We know it from The End and Let It Bleed, and since then we have been shown nothing new. The fact that Dean can't kill his brother? Was it supposed to be a revelation? That they keep each other human? Isn't it clear from season 5? It seems to me a mistake when they started to tell Dean's story from Dean's point of view. When it was Sam's story told from Dean's point of view it was balanced because it left us with two main characters and compelling because it left a lot to interpretation. But Mark of Cain was Dean's story and they told us this story from Dean's point of view. And it greatly reduced the interest to the potentially great storyline. It's like a story of Dr.Watson told from the point of view of Dr. Watson by Dr. Watson.