Re: "Clearview doesn't want to come defend its technology in court"
Firearms identification wasn't my area* however I note that the tests were based on new firearms and the whole basis of marks examination is that an object which makes a mark picks up unique characteristics over the course of time so that an old object will leave a mark with more identifying characteristics than a new one.
It also concerns me that a lot of effort in these reports seems to have gone into the inconclusive responses. To my way of thinking there are only three possible responses to a comparison: they could match, they couldn't match and I can't draw a conclusion. The last shouldn't really affect the court's decision. Also, "could" and "couldn't" carry very different levels of confidence. If a particular blood sample couldn't have come from some particular person the court could reasonably decide it didn't. If it could that doesn't mean must have** and the court should take into consideration that it could also have come from many other people and should be provided with frequency figures to decide whether, in the particular circumstances of the case, that was likely.
But returning to this case - "thinking" the gun was responsible shouldn't be enough. Thinking isn't evidence and if that's all they were offering it suggests they didn't have evidence or even that they had evidence agianst them.
* Fortunately. One of the very few times I was asked to look at a firearm for some other purpose it turned out to have been booby-trapped. That was spotted by the colleague who examined it. A similarly booby-trapped forearm exploded and killed two police officers who'd opened it.
** I have experienced prosecution trying to drag "could have" on a hair sample into "must have". The FBI had a reputation for claiming great success in matching hair. I couldn't understand it because I never found it very conclusive. I later read that a proper investigation trashed that reputation. The only situation where I found hair examination could become conclusive was in the identification of three very badly burned bodies where a sample recovered from one was compared with samples from the hair brushes of the known victims and fortunately could only have come from one.