Police obtaining your DNA without a warrant is one issue in this case. That’s allowed if you go out in public or don’t incinerate your trash. Once in the dumpster, there is no “expectation” of privacy. The other issue is law enforcement’s easy access to commercial ancestry DNA registries to round up relevant DNA profiles from either yourself or your relatives. “All OK for the Greater Good,” I suppose.
Start this video at 42:00. The first part is PR for the investigators in the “Justice Team” assembled to look for this guy.