When a small black Nissan Sentra was found submerged in a shallow canal in eastern Ontario on June 30, 2009 with four dead females inside – members of the Shafia family – investigators had one critical question: Was it a freak accident or a heinous murder? Key to teasing out the answer was a meticulous analysis of the Nissan, another Shafia vehicle – a Lexus SUV – and the scene at the canal. Constable Chris Prent, a provincial police officer and collision reconstruction expert, produced a detailed 94-page document. In it, Prent revealed his conclusion: The Nissan was deliberately pushed into the canal by someone operating the Lexus. This theory was the centrepiece of the criminal case that saw three members of the Shafia family – Mohammad Shafia, his wife Tooba Yahya, and their son Hamed – each convicted by a jury of four counts of first-degree murder. Constable Prent’s 94-page document, titled An Analysis of the Events at Kingston Mills Locks (Rideau Canal), City of Kingston – was not given to the jurors. The 12 people who decided that the Shafias were guilty of mass murder did not see the document.