On November 10, 1991, black smoke rose from a house and into an early-morning sky over Fort Stockton, a small town just west of the Pecos. A 44-year-old woman with big green eyes paced her front yard in the fall air, hysterical, wearing nothing but the nylon nightie she slept in. Through the picture window that looked onto the street, lit with orange tongues of fire, the person she was closest to in the world—her uncle Bill Roscoe Richardson—lay inside, dead or dying. The fire had begun in the living room. A hole in the ceiling acted like a flue, drawing scalding gases through the attic and down into other rooms.
Sonia Cacy had escaped through her bedroom window and run from one neighbor’s home to the next, pounding on doors, the only thing moving on a darkened, sleeping street. As neighbors emerged and police and firefighters arrived, the story that would shape the rest of her life was solidifying. The desperate attempts to plunge back into the house, forcing first responders to restrain her. The punch she threw at the victim services coordinator. The confused details about how exactly she woke up. The district attorney would eventually read the hostility of an arsonist in these details. Years later, others would come to see the infinite variability with which a human may respond to trauma. They would identify what might be a sad but pedestrian explanation for all of it.
Even as she was admitted into the hospital after the sun rose, coughing up black sputum and vomiting repeatedly, the narrative was calcifying. Investigators saw the deep burns in the carpet as evidence of an accelerant. Her behavior that morning signaled guilt. The appearance of a couple of unexplained fires at the house after Cacy moved in gave them a pattern of behavior. A hole in the drywall near the body was construed as damage caused by a man writhing in agony. And the papers that named her the sole beneficiary of Uncle Bill’s meager estate provided motive.
At trial, the evidence against her looked unassailable to a jury. A toxicologist from the Bexar County forensic lab even testified to the presence of an accelerant like gasoline in scraps of clothing from Uncle Bill’s body. It took them two hours to convict her of murder. She was sentenced to 55 years in prison.
And she might still be locked up if not for a Cambridge-educated chemist and inventor named Gerald Hurst. When he cracked open Cacy’s file in the spring of 1996—three years after her conviction—he was appalled by what he found.
If there was a moment when fire investigation began to emerge out of the dark age of hunches, untested hand-me-down arson indicators, and wives’ tales, it occurred when Hurst turned his attention to Cacy’s case. A tall, lanky man with a wiry beard and deep-set eyes, Hurst once developed weapons of war, but when he shifted careers in the seventies, using his background in chemistry to become a fire expert, he waged intellectual warfare against questionable science presented in civil trials. He had never been involved in a criminal proceeding before looking into the Cacy file, but he understood the chemical reaction that produces fire, and he was horrified by the quality of arson science used in the testimony that led to Cacy’s conviction.
And it wasn’t just the hard science that seeded his doubt—it was the bond between her and Uncle Bill. Everyone who knew them spoke about it with a certain awe. She called the man Daddy as a child until she learned it stung her father. She grew up listening to him play his steel guitar at night on the porch. When she had a family of her own, she moved them into a shack without running water near the New Mexico line, close to where Uncle Bill lived as he wrung the last drops from an old stripper well too played out for the oil company to mess with anymore. And before he died, she had moved in with the old man at his house in Fort Stockton as his health