It All Comes Down to Space: The Forensic Potential of CCTV

The visual capacities of CCTV cameras are inextricably tied to space: the space they capture in their frames versus the space that falls outside their ranges. The camera eye also conditions the knowledge that viewers can gain from the surveillance footage: the space CCTV analysts do not see is a space they do not know. Even within the field that the camera covers, space can become the decisive tool for making monitored information meaningful. The American true-crime series Forensic Files (Season 11, Episode 30, 2007) depicts how so-called photogrammetry uses the architecture surrounding a perpetrator on CCTV in order to establish the criminal’s height.

The TV show, itself sensationalist, traces the matter-of-fact methods of scientific experts for solving seemingly unsolvable offences. In an episode titled “A Tight Leash,” the car of a murdered woman is left on a supermarket parking lot in the early morning. Investigators assume that the murderer entered the store to avoid stirring attention by simply leaving the lot. They notice a suspicious man on the supermarket’s surveillance tape. Cunningly or coincidentally, the man outwits the CCTV’s visual capabilities. He does not clearly show his face to the lens or give away distinctive body features as he wears a large dark parka and a wool hat. The technology’s restricted optical quality renders the security tape too grainy to identify physical details. Enter the photogrammetry specialist who declares that the footage of the suspect is still useful if analysed in connection to the store’s floor tiles which the wanted man traverses.

As the narrator explains, “[p]hotogrammetry is using a two-dimensional photograph to create a three-dimensional image. And it’s done with mathematics and physics.” The photogrammetrist isolates a frame grab in which the stranger’s feet and the grid pattern of the tiles align. The body is at a right angle to the tiles. The expert calculates the man’s height in relation to the tile size by placing a vertical line with a scale along the body. Thanks to the architecture surrounding the suspect, the visual information about that suspect becomes readable. Architecture puts into perspective what we see.

As the show clarifies, other pieces of evidence are necessary to determine who the man on tape is and that he is guilty of homicide. Yet the photogrammetric analysis is a relevant piece of the puzzle. The CCTV footage does not only help to prove the culprit’s physical identity but also that the built environment is significant for surveillance technologies to work.