Good question. Could also lead to finding out who actually killed that ex Russian spy. If the nerve agent was dumped in that dumpster, it could leave residue that lasts a long time. I don’t know how long that stuff lasts. A minuscule remnant could be enough to kill someone.
If somebody dumped the stuff in that area they could narrow it down.
Too bad they couldn’t find out from the woman where she’d been rooting around, but maybe now all the dumpsters in the vicinity could be chemically tested.