Helena Greenwood dedicated part of her career to discovering the unique identifier in DNA that revolutionized forensic science. Years later, this same innovation helped convict his killer.
In 1985, Helena Greenwood, a pioneering British biochemist, was brutally murdered in her Southern California home. This crime remained unresolved for more than a decade, until advances in DNA technology – a field to which Greenwood had dedicated much of his career – eventually identified his killer.
Greenwood, a graduate of the University of Sheffield and a PhD in biochemistry from the University of London, moved to the US with her husband in 1977. She started working at Syva, a medical diagnostics company, before moving to Gen-Probe in San Diego, a biotechnology startup focused on DNA-based diagnostic methods.
Her tragic end began in 1984, when she was attacked in her home by David Frediani, a financial analyst with a history of robberies in wealthy neighborhoods. Frediani pointed a gun at Greenwood and attacked her before fleeing. Despite a police investigation led by Sergeant Stephen Chaput, no arrests were made at the time. Forensic samples were collected, but the technology available at the time did not allow for the identification of a suspect.
At Gen-Probe, Greenwood was captivated by developments in “DNA fingerprinting”, pioneered by geneticist Alec Jeffreys at the University of Leicester. Jeffreys had discovered that variations in “junk” DNA they could serve as a unique genetic identifier for individuals, similar to a barcode.
In March 1985, Jeffreys published his findings in Nature and Greenwood immediately realized its potential, urging his company to pursue this revolutionary technology, anticipating its implications for forensic investigation and diagnosis.
Shortly thereafter, Chaput received a tip about Frediani, whose fingerprints matched those found in Greenwood’s home. Although technology was unable to confirm Frediani’s DNA at the time, Greenwood’s testimony and circumstantial evidence led to a trial.
However, Frediani was released on bail and, tragically, Greenwood was murdered in August 1985before being able to testify in court. His body was found in the garden of his new home in Del Mar, California, and forensic evidence has failed to establish a conclusive link between Frediani and the crime, writes .
Frediani served a reduced sentence on lesser charges unrelated to Greenwood’s murder, but in 1999 the case has been reopened as part of a San Diego project that reexamined unsolved cases with new DNA technology. The technique that Greenwood had championed in life now offered a chance to solve his murder.
Forensic scientists reanalyzed samples and DNA recovered from Greenwood’s fingernails matched Frediani’s profile. This time, DNA evidence they definitively placed him at the scene of the crimeallowing a conviction that had eluded investigators for 14 years.
In 1999, Frediani was convicted of first-degree murder, with DNA analysis revealing a one in 2.3 quadrillion chance that his DNA would match any other person. His conviction constituted a important milestone in forensic science and highlighted the transformative power of DNA technology in achieving justice, even years after a crime has occurred.
