Complex sentence: Further testing on the knife produced inconclusive results, due in part to the rather small amount of blood, and because both John Mark Byers and Chris Byers had the same HLA-DQα genotype.
Split into simpler sentences: Further testing on the knife produced inconclusive results about the source of the blood. Uncertainty remained due to the rather small amount of blood and because both John Mark Byers and Chris Byers had the same HLA-DQα genotype.