and (for them) unheard-of technique in rape investigation. The process was very difficult to explain – and the exercise of sending samples to a U.S. lab would leave little change from $20,000.

The Birth of DNA Fingerprinting

During the period in which the Narong Road rapist had been operating, a UK-based scientist had made the most dramatic discovery in the entire history of forensic science. In 1984, University of Leicester molecular biologist Professor Alec Jeffreys had developed a technique he called DNA fingerprinting.

DNA (or deoxyribo- nucleic acid) is a long double-stranded spiral molecule coiled inside the nucleus of most human cells. It is composed of four different molecules, which scientists often describe as chemical “letters” in a four-letter alphabet. These “letters” (actually the building-block molecules adenine, thymine, guanine and cytosine)police came to Jeffreys for help with two unsolved murders. In 1983, a 15-year-old schoolgirl had been raped and murdered in the small village of Enderby. In 1986, when another teenage girl was raped and murdered in a strikingly similar way in the nearby village of Narborough, police had arrested a 17-year-old youth who had been working as a kitchen porter at a local mental institution. The youth had been spotted near the murder scene on several occasions, had a history of molesting children, and couldn’t give police a reason for his presence near the lane where the girl’s body had been found. Already emotionally disturbed, the intimidated teenager cracked under the pressure of the police questioning and confessed to the second murder. But he continued to frustrate