ATLANTA — The yellow pills had already killed four before landing in Brian Hargett’s lab last month. They were clearly counterfeit — the letters P-E-R-C-O-C-E-T were as crooked as the dealer who had peddled them throughout central Georgia — but now his chemists had to figure out exactly what they were. And fast. Lives were still at stake; health officials wanted to alert the public about the phony pills. First, though, they had to know what was in them.

At the Georgia Bureau of Investigation’s forensic lab outside Macon, Hargett assigned the tablets to one of his forensic chemists. She threw on her gown and gloves, weighed a pill, and dropped it in a skinny vial to soak in ethanol. Then she ran a test designed to separate and identify each substance in the pill. Two synthetic opioids showed up — including one never before seen in Georgia.

Their best guess: the little-known, and lethal, compound known as cyclopropyl.

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