"Mixed blood" refers to the claim that Amanda's blood was mixed with Meredith's blood in five places in the cottage, outside of the murder room.
I believe it was claimed by Mignini during the 2009 trial. Whether that be true or not, Judge Massei's motivations report emanating from that trial, released in 2010, is clear - he says that Amanda's "biological material" is mixed with Meredith's blood in those locations.
If there had been verified mixed blood from the two, then I would be a guilter.
No one of any credential whatsoever these days claims "mixed blood". The Machine/Harry Rag includes this factoid in his comments-bombs to comments sections of articles.
Guilters used to make up other factoids about Amanda, to explain how her blood got at the scene... which (with the exception of the bathroom faucet) none was found. Guilters talk about the "hickey" on Knox's neck being a source for this blood-letting on her part. Knox was photographed upon her arrest on Nov 6, and there is a faded spot there on her neck, and the police photograph has an endorsement on it saying that it was in some sort of false colour, so that the mark would be visible. If this had been a source of blood 4 1/2 days previous, the mark would not be in that condition.
Guilters then shift gears saying that Meredith must have belted Knox in the nose during the imagined attack. This would explain why there is not mark visible on Amanda to show this fantasy blood's source. Guilters never explain why, then, Amanda's blood is not found in the murder room from this injury.... and nowhere in the cottage un-mixed with Meredtih's.
It's a factoid that did not survive even the first convicting judge's motivation's report.
Further to this, Judge Massei never explains why it would be forensicly interesting only to find "biological material" (hair, dried skin sluffed off....) Massei says that the material found in the bathroom from Knox must be there from the action of her cleaning Meredith's blood off of herself.
That is simply a ludicrous claim, as ludicrous as the "mixed blood" even Massei says is not there!
It's that part that leads some, me included, to believe that Massei wrote his motivations report so that the verdict it was supposed to support would be overturned. Otherwise I have no explanation for why a seemingly compis and mentis judge would find it unusual to find biological material of one of the cottage's occupants at the cottage they lived in - particularly in the bathroom she and the victim shared!
Mixed-blood: game over... I'm a guilter and I would be making guilt-like assertions here simply to bait innocenters. But the notion of mixed-blood died with Massei.
That Andrea Vogt would have this as part of her BBC3 documentary shows where her biases lie.