Ed Rybicki, a virologist at the University of Cape Town in South Africa, answers: Tracing the origins of viruses is difficult because they don't leave fossils and because of the tricks they use to make copies of themselves within the cells they've invaded.Some viruses even have the ability to stitch their own genes into those of the cells they infect, which means studying their ancestry requires untangling it from the history of their hosts and other organisms.There are six key steps that tend to characterize the scientific method. This is the part where a scientist proposes the problem that he or she wants to solve.A well-conceived question usually leads to a hypothesis, a potential answer to the question at hand. The scientist predicts what the outcome will be when he or she tests the hypothesis.of 2002, Carol Batie was sitting on her living-room couch in Houston, flipping through channels on the television, when she happened to catch a teaser for an upcoming news segment on KHOU 11, the local CBS affiliate. “I scared the kids, I was screaming so loud,” Batie told me recently. ’ I knew that all these years later, my prayers had been answered.”The subject of the segment was the Houston Police Department Crime Laboratory, among the largest public forensic centers in Texas.By one estimate, the lab handled DNA evidence from at least 500 cases a year—mostly rapes and murders, but occasionally burglaries and armed robberies.
Josiah Sutton with his mother in 2003, a week after his release from prison.
Acting on a tip from a whistle-blower, KHOU 11 had obtained dozens of DNA profiles processed by the lab and sent them to independent experts for analysis. “My son is named Josiah Sutton,” she began, “and he has been falsely accused of a crime.” Four years earlier, Batie explained, Josiah, then 16, and his neighbor Gregory Adams, 19, had been arrested for the rape of a 41-year-old Houston woman, who told police that two young men had abducted her from the parking lot of her apartment complex and taken turns assaulting her as they drove around the city in her Ford Expedition.
The results, William Thompson, an attorney and a criminology professor at the University of California at Irvine, told a KHOU 11 reporter, were terrifying: It appeared that Houston police technicians were routinely misinterpreting even the most basic samples. A few days after reporting the crime, the woman spotted Sutton and Adams walking down a street in southwest Houston.
From the beginning, Sutton and Adams denied any involvement.
They both had alibis, and neither of them matched the profile from the victim’s original account: She’d described her assailants as short and skinny. Sutton was three inches taller and 25 pounds heavier, the captain of his high-school football team. Having seen enough prime-time TV to believe that a DNA test would vindicate them, Sutton and Adams had agreed, while in custody, to provide the police with blood samples.