If we lose public trust, we will lose this tool

Naw. It's clear public trust is completely unnecessary.

How common these practices are remains unknown

Let me mansplain this to you... police will do anything they want because the legal system will never challenge them. Therefore, police will use any practice they want, when they want and how they want. It's extremely common.

If we can’t trust these practitioners, we certainly cannot trust law enforcement.

No!!!!

It's impossible to not leave a trail of DNA everywhere one goes. If they can't do it already, I suspect that soon they will be able to get a DNA sample from ones exhaled breath. Brave New World is here. It's already too late to "put the genie back in the bottle."

The VA always collects DNA from everyone they treat using blood samples. The fine print someplace says it is for "scientific studies" and consent is already given by the original consent to be treated at VAMC.