My fear is that planting DNA isn't something individuals are likely to do (thought it's not impossible), but something the state or large organizations are likely to have the resources to do properly. Corrupt LEOs. Corrupt politicians. It seems a lot easier than many alternative corrupt practices.
Historically there have been some pretty bad abuses in court over the accuracy and reliability of dna evidence, with some convictions that had to later get overturned.
Not trying to be gross, just trying to shine light on the idea that judges are in a difficult situation. They have to consider fairness for all parties involved.
Justice can't just be about catching people it has to also weigh the cost of false positives and the effect that the methods have on society.
It's a constant issue with things like TOR, encryption, and alt currencies like BTC. They can do a lot of good for repressed people but they're also inevitably going to be used by people most people would agree are awful people to protect themselves from justice. If you're developing those tools you have to be ok with that just like we have to decide as a people where we're ok with the balance between preventing crime/catching criminals and personal liberty and privacy.
Why would someone be less concerned with the reliability of the criminal justice system in that case? A low standard means it is easier for the government to let the guilty go free while making a show of punishing someone convenient.
It makes sense that people who suffered from a crime would emotionally prefer more focus on a correct conviction at the cost of more false positives.