And when a presumptive test is negative there is no point in taking any confirmatory tests. A negative DNA test is obviously not conclusive otherwise there wouldn't be any need for further tests after that. Luminol test came first, second the DNA test, third the TMB test. The DNA that was found was LCN and only tested once IIRC. So very small amounts which is in line with the negative TMB test. Negative TMB test is not conclusive either. Overall, there is no conclusive blood test and the assumption that it is blood is not a scientific issue. It is a CSI issue. JMO.
If not blood and not DNA, then what was AK doing that was do nefarious w those footsteps?