Dogs will be irrelevant soon enough anyway. X-ray diffraction can accurately identify specific materials based on molecular signature, and easily penetrate small packages, foil bags, stuff buried inside
other materials. Anything short of a thick metal box. The only limitation up to now has been speed. Here are the new Smith's Detection XRD scanners at the recently completed JFK International Mail Facility.
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They're still relatively slow (.2 meters / second belt speed) , and packs will have to be targeted (based on the new post de minimus detailed customs data required for each pack, and AI algorithms determining suspiciousness) to be run through these, but once they come online the number they've installed will be like increasing hand inspections 1000x over what they can open and inspect currently.