The technique of blood-spatter analysis was pioneered by chemist Herbert MacDonell, who trained himself in an unaccredited homemade lab in his basement, because he believed he had a “natural scientific attitude”. He then went on to train hundreds of others. His published findings claimed that blood patterns could show exactly where a victim or perpetrator were positioned at the time of a crime and how the wounds were inflicted. From the 1980s onwards, Herbert became the go-to blood expert to give trial testimony. He would theatrically demonstrate to the court using props such as vials of his own blood to reveal what had happened at the crime scene. He became something of an celebrity, and juries were dazzled. In time, however, defence attorneys began to argue that he could not replicate what actually happened during a murder. A 2009 National Academy of Sciences report found that “some experts extrapolate far beyond what can be supported”, and that the “uncertainties are enormous”.
ONE MOTHER’S TRAGEDY
In 1997, single mother Julie Rea woke at 4am to the sound of a scream. Rushing into her son Joel’s room, she found a masked intruder. She fought him and chased him out of the house. But her ten-year-old boy was dead, stabbed 12 times, twice through the heart. Police failed to adequately preserve the crime scene and extracted no fingerprints from the weapon used, a knife from the family kitchen. Detectives were solely focused on one suspect: Julie. “Su
