Twenty-four years after
he provided crucial testimony that helped send a man to Texas’s death row, DNA expert William Watson has recanted his opinion and called out Harris County prosecutors — including an assistant district attorney turned true-crime TV star — for distorting his conclusions to win a conviction.
In a
new court filing
seeking to overturn Jeffrey Prible’s 2002 conviction for the murder of a Houston family, Watson said he would never give the same testimony today. “Based on … changes in the field and my own increased experience and scientific knowledge, if I were asked to testify today, my answers to many of the questions asked by the State at trial would be different,” he wrote in a
declaration
filed on August 28. “Today I would provide more thorough and nuanced explanations.”
Watson also wrote that prosecutors “misrepresented” his testimony in both their opening and closing statements, and made “inflammatory” remarks that twisted both the science and his opinions.
Prible was accused of murdering his friends Steve Herrera and Nilda Tirado, who were found shot to death at their home in North Houston in 1999. A fire was started in an apparent attempt to cover up the crime; the couple’s three young children died from smoke inhalation. Prible had been hanging out at the couple’s home in the hours before they were killed, which made him an early suspect. But there was no evidence linking him to the scene — save for a DNA sample taken from semen collected from Tirado’s mouth. Prible had an explanation for this; as he told investigators at the time, he and Tirado had been having an affair behind Herrera’s back, and she had performed oral sex on him earlier that evening.
The case went cold until Harris County Assistant District Attorney Kelly Siegler took it over, reexamining the evidence and concluding that there was no innocent explanation for the presence of Prible’s DNA. Instead, Siegler decided, the semen was evidence of a brutal sexual as
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