Australia's "drug sniffer" dogs

When Australia's "drug sniffer" dogs indicate sniffing drugs, 75% of the time the following search does not find any drugs.

• Maybe drug mules have adopted a clever new way to hide the drugs, so dogs can sniff them but humans can't find them.
• Maybe these dogs do a bad job.
• Maybe all "drug sniffer" dogs do a bad job. How would we know?
• I've read that the cops that control the dogs actually decide whether to report that the dog "sniffed drugs" on any given person. Maybe these cops make that decision based on a whim to harass certain people, and maybe those people mostly don't carry any drugs.

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