New observations on the interactions between evidence and the upper horizons of the soil

Abstract

Since Darwin's work on the movement of objects in the soil due to earthworm action, interest has continued in determining how bioturbation affects the archaeological record. The work of Darwin is being continued with an additional focus on forensic implications of evidence moving over time. The actions of earthworms and the rates at which they cause small objects to sink into a given soil environment is predictable. Objects can accumulate over time on buried horizons, where once the horizon is identified they can be recovered. Small objects disappear from view in certain outdoor environments in a short timeframe with respect to forensic considerations. Experiments are being undertaken to test rates of sinking. Normal visual search techniques do not locate such evidence. As well as earthworm action, maggot masses feeding on a cadaver can rapidly cause small objects and bone to sink from view. The effects on vegetation growth and soil colour from decomposition of a body can indicate the primary deposition site of the body, even if it has been moved or dispersed. Case studies demonstrate how specific archaeological techniques have been used to maximise location and recovery of important evidence. Methods for consideration by Senior Investigating Officers suggest specialist professional support for some crime scene examinations will benefit forensic investigations.