I think the coin-flip analogy comes from the idea that once an officer thought you had drugs, he/she was about 55% right (not accounting for false negatives). T

I think the coin-flip analogy comes from the idea that once an officer thought you had drugs, he/she was about 55% right (not accounting for false negatives). The dog alerted most of the time, thus allowing for search to confirm or deny the suspicions. Thus the dog gave no real information and the officer was the coin, but the reporter conflated these success rates.