How a $2 Roadside Drug Test Sends Innocent People to Jail

Amy Albritton can’t remember if her boyfriend signaled when he changed lanes late that August afternoon in 2010. But suddenly the lights on the Houston Police patrol car were flashing behind them, and Anthony Wilson was navigating Albritton’s white Chrysler Concorde to a stop in a strip-mall parking lot. It was an especially unwelcome hassle. Wilson was in Houston to see about an oil-rig job; Albritton, volunteering her car, had come along for what she imagined would be a vacation of sorts. She managed an apartment complex back in Monroe, La., and the younger of her two sons — Landon, 16, who had been disabled from birth by cerebral palsy — was with his father for the week. After five hours of driving through the monotony of flat woodland, the couple had checked into a motel, carted their luggage to the room and returned to the car, too hungry to rest but too drained to seek out anything more than fast food. Now two officers stepped out of their patrol car and approached.

Albritton, 43, had dressed up for the...