DNA in theory is very simple. It is much harder when you got a mix of multiple unknown donors, contaminated or decayed samples. Problems quickly occur when they then apply some "computer algorithms" to puzzle together things to create a probabilistic match. It is those proprietary black box computer algorithms that are being heavily discussed in courts, not the theory of DNA.

If we removed all cases that involved multiple unknown donors, contaminated or decayed samples, then DNA evidence would be much safer and open and we wouldn't need those proprietary computer algorithms. It would also significant reduce the number of cases where DNA evidence is used.