If there is indeed a piece of physical evidence which ties the two people together, it's pretty compelling to me. Not definitive, but compelling. Anyway far more so than "this guy is a butcher so he would have been bloody all the time; therefore he did it."
No doubt. Well, as I noted above I've always thought the best suspect was Kosminsky based on Inspector Abilard's investigation and I never heard of the DNA study until just now.