Using GIS and digital aerial photography to assist in the conviction of a serial killer

Abstract

A desktop geographical information system (GIS) was used to pin-map the 86 cases associated with the Wemmerpan serial killer, representing crimes committed between 17 September 1995 and 19 December 1997 in central, western and southern Johannesburg, South Africa. The crimes ranged from murder and rape to assault with intent to cause grievous bodily harm. A series of maps were produced, using either digital street-map data or ortho-corrected digital aerial photographs as the backdrop. The photographs were particularly useful for incidents that occurred around Wemmerpan itself, a popular recreational area consisting of a dam (Wemmerpan) surrounded by picnic areas, a small forest, open ground, mine dumps, footpaths and other geographical features not normally found on a street map. The maps were used in court to show the geographical extend of the serial killer's activity space and to help the court understand the sequence of events as evidence was led. Historically, photographs of a wall map bedecked with stickers have been used in such cases, but they have proved to be unsatisfactory. The digital maps are much more flexible, versatile and easier to use.