When did she say this? I don't doubt she said it, but that is no reason not to check those knives.
Please explain why in the world after Amanda's statement about Patrick and the arrest of Patrick that the police didn't bring in his knives for testing. He was the killer, not Raf, not Amanda.
Patrick had many items seized from his apartment, there is a long list of pices of clothing and shoes, plus a cell phone and a phone care.
He also described the police being very curious about his kitchen cutelry, I think he said that in an interview, maybe his interview by Panicucci on TG Cinque.
However, I don't know about knifes seized at his apartment. They might have been collected but I don't know about this. Maybe they didn't find any one suitable as a weapon.
His bar instead was seized as a whole, sealed, but no one had entered yet and items were not collected from the inside.
However, no item from Lumumba was tested for DNA as far as I know, since on Nov 13. it was already clear that he had nothing to do with the crime and a written communication about this was forwarded by Mignini.
As for the knife in Kercher's apartment, they were seized and photographed. However, I think they were not tested, my personal inference about that was that, given that they were basically clean, a DNA test would not have been probative, since they were in Kercher's apartment after all. I mean Meredith's DNA inside Meredith's kitchen may be a non-probative finding from start.