Here are factors assisting SAR’s decision on where to search for a disposal site of a victim.
From - Detection of Body Dump Sites and Clandestine Burials: a GIS -Based Landscape Approach by Hector A. Orengo
http://docs.google.com/viewer?a=v&q...ar6iUO&sig=AHIEtbSumiusggvnfGz0Mmppr0YovkcE_Q
"1) Carrying of a corpse will necessarily require the use of a covered, motorized vehicle to the vicinity of the dump site. It has been commonly asserted that the majority of corpses have been found in close proximity to roads or parking areas (Streed 1989, in Killam 2004:17). Therefore, a search following the road network will have many more probabilities of success than a normal extensive search (Rossmo 2000:130).
2) Due to physical limitations, the usual distance covered dragging a body is about 50 ft on plain terrain (McLaughlin 1974:28, Morse et al. 1983:6). Keppel and Birnes (1995) have estimated the maximum distance to carry a body to 150 ft, even though, they agree with the 50 ft estimate as the usual distance. Following Burton (1998), Rossmo (2000:130) states that child bodies, being much lighter, can be carried for 200 ft. Of course, this will vary depending with the slope, kind of terrain, vegetation, and other factors. Effectively, 90% of the bodies are recovered downhill because it is easier for the offender to drag the victim (Sacks 1999; Hunter 1996b:92; Robbins 1977; Cherry and Angel 1977). The fact that from the road the visibility downhill is poor can be equally important regarding the offender’s choice of going downhill.
3) Terrain slope can be also very important when the body is buried: an excessive slope will render difficult the process of digging a grave.
4) As Killam (2004:17), following Streed (1989), has noted, “bodies are usually found off the right passenger side of the road, outbound from the city or town.” That is an important clue: knowing the departure site of the offender is important in order to give priority to the passenger side of the road in body search activities.
5) Most disposal sites are located within a 30-45 minute drive from the place where the body was picked up (Streed 1989, in Killam 2004:17). As Rossmo (2000:174) has shown, those sites are located at a mean distance of 33.7 km from the crime site. Fifty percent of those were located at more than 20 km. This data shows the wider distance range of body dump sites to which, consequently, is difficult to apply distance-decay parameters.
6) Lakes, deep rivers, and canals traditionally have been disposal points (Killam 2004:16, 18). Returning to Rossmo’s analysis (2000:175), of the 104 body dump sites considered, 20.2 % were located in rivers, lakes, or marshy areas.
7) Other places in which people are prone to hide bodies are wells, shafts, mines, or any other pre-existing hole (Killam 2004:16, 18; Levine et al. 1984)
8) It is possible to map those areas in which burial is feasible according to soil profile, land use, and underlying geology (Hunter 1996a:17 and 1996b:92).
9) Obviously, the most feasible place to look for a victim’s body will be determined by the crime’s particular circumstances. The first places to investigate will be the suspect’s properties (Killam 2004:14), mainly his or her residence. For obvious reasons, residences are not included in this project. Other urban areas are regarded as having low clandestine burial potential due to the high chance of the offender to be discovered.
10) As Killam has suggested (2004:18), dump sites will be out of sight of neighboring houses, but, as bodies are usually discarded at night, they have to be easily accessible in the dark."
On #5, distance is calculated differently for child abductions. The location of the site increases as the age of the child rises.