One of the most difficult things criminal investigators can face is locating a corpse that has been dumped in a remote location. Large number of searchers will fan out in any area where the body might be and spend many hours and days searching, often without result. Cadaver dogs can help in that they can detect the odor of decomposition, even in buried corpses. Arial infrared scanning can also be useful since a decomposing corpse tends to produce heat, which the scanner can detect against the cooler background of the surrounding soil. Also, aerial photography can help by indicating areas where the natural vegetation has changed in some way.
A decomposing corpse can initially produce a toxic environment for plant growth and can therefore make the vegetation less lush in that area. As the decomposition process progresses however it often serves as fertilizer and enriches plant growth so that they are greener, more lush, and appear different than the surrounding growth. Aerial photography can often detect this.
A new technique has been developed by scientists at McGill University. It is called Hyperspectral Imaging. It is similar to aerial photography but more sensitive. It also can be useful over a longer period of time.
Initially the chemicals of decay released by the body can inhibit plant growth and alter the way light is absorbed or reflected by the plants near the burial site. Early on they don’t reflect visible and infrared light as well but after several years they tend to reflect light much more readily. This new hyperspectral imaging system can detect these differences and therefore locate the burial site. Burial sites as old as 50 years have been detected using this technique. Exciting stuff and it will be interesting to see how this develops.
For more on locating and then identifying corpses check out my book Howdunnit: Forensics.