I believe the SC ruled that any discarded cup, straw, chewing gum, etc can be scrounged and tested to see if the dna found at the crime scene matches the suspect’s discarded stuff. Once he discards it, it is fair game, no court order needed.
For a capital offense, I doubt very much that a scrounged DNA sample would be admissible as evidence.But it might help in getting a court ordered DNA sample from the accused.
This has all yet to play out, but this will not be an open and shut case for the prosecution just yet.