Only if you substantially rule out the possibility that all 3 were involved in the murder.

Why should we privilege that hypothesis?

ETA: Besides, the claim on the table seems to be that if you look at the case without DNA evidence; and then ADD DNA evidence, it would substantially reduce, basically to zero, the assessed chances that Knox and Sollecito were involved in the murder. Agreed?

No. Or at any rate, that's not an interesting claim, so I don't see why it should be on the table.

There was an abundance of physical evidence of Rudy Guede on the scene. If Knox and Sollecito had any physical involvement with the crime, they should have left biological evidence on a similar order, but in fact tests for evidence of their involvement did not return positive results except when corrupted by serious mishandling and poor testing procedures. The knife and bra clasp were major pieces of the prosecution's case because they alleged that they held genetic evidence implicating Knox and Sollecito, but in fact they did not, and even if they had carried evidence of Knox and Sollecito, it would have been a suspiciously small amount of evidence compared to what one would reasonably expect had they actually been involved.

Think of the allegation of Knox and Sollecito's involvement in the murder as a claim that there is an elephant in a room. Another party examines the room and finds...

X: Well, there does seem to be an elephantish sort of smell in the room, but it's otherwise devoid of large mammals.

Y: But you agree that it's a distinctly elephantish sort of smell?

X: Yes, it does smell much more like an elephant than anything else I can think of.

Y: In that case, the presence of an elephant makes it far more likely for you to observe this smell than the non-presence of an elephant, therefore it meets the bayesian definition of evidence, so you must revise your belief in the presence of an elephant upwards!

X: But hiding an elephant in a room is very difficult. If there were actually an elephant in this room, I would expect a lot more evidence than that. I can't think of any plausible way that you could get an elephant in here and hide every sign of its presence but its smell, only very implausible ones. Your claim was sufficient evidence to promote the hypothesis of an elephant in this room to my attention in the first place, so this is less evidence than I need to maintain my prior uncertainty. To maintain my prior uncertainty, I would need to observe evidence that gave significant reason for suspecting the presence of an elephant, such as this smell, while finding some sort of arrangement that could plausibly hide an elephant. This, on the other hand, is a small enough amount of evidence that I must revise my confidence to near certainty against.

It is reflective of a suspiciously poor case that the prosecution brought so little biological evidence against Knox and Sollecito compared to the one person we can be almost certain was actually involved. The pieces of evidence were mishandled, making them suspect to begin with. This provided an opportunity for us to make our beliefs pay rent. Given the state of the evidence against them, most of us on this site concluded that Knox and Sollecito were probably not involved in the murder, so the biological evidence brought forward by the police was probably not contingent on their presence at the crime, but due to subsequent corruption and mishandling of the evidence. Thus, we could predict that the independent experts' review of the evidence would find that when properly processed, it did not point to Knox and Sollecito's presence at the crime. If the evidence were contingent on their presence at the crime, we would not expect to observe this.

So do you concede that your high confidence in their involvement did not predict observations as well as our belief that they were probably not involved?