In the early 1990s, police departments across the country begin employing DNA testing technology in investigations. (Scientist Alec Jeffreys developed the technology in 1984 when he “discovered DNA fingerprinting” (100).) Both state and federal governments create databases of DNA profiles, collecting both the DNA of known criminals and the crime-scene DNA of uncaptured suspects. While DNA can provide key evidence in identifying a murderer or other criminal, the testing process is slow, the analysis of a single profile sometimes taking weeks.

In 1996, the Orange County police department sends DNA samples to the California state’s DNA lab, revealing the culprit behind six unsolved murders. Ecstatic at the possibility of DNA evidence, Orange County criminalists begin reexamining unsolved cases, hoping that DNA testing might open new leads. Criminalist Jim White remembers his suspicion that the Harrington and Witthuhn murders were connected, and instructs his fellow criminalist Mary Hong to analyze the DNA evidence taken from both crime scenes. By analyzing the DNA with the new PCR-STR (polymerase chain reaction with short tandem repeat) analysis, Hong determines that a single individual committed both the Harrington and Witthuhn murders. Further, Hong discovers that the same culprit also committed the murder of Janelle Cruz in 1986; police hadn’t yet connected that murder to the other two.