Identification of some factors influencing soil transfer on shoes

Abstract

In criminal activities, soil can be transferred from a crime scene to items linked with a perpetrator; for example, shoes, cars or tools. Several parameters will influence the quantity of soil transferred in a given scenario. The knowledge of the most influential factors can help the expert to assess the evidence using a logical approach at the activity level or to predict the amount of soil that can be expected in a given scenario. The influence of five chosen parameters, namely the shoe profile, shoe size, walker's weight, soil type and soil humidity were assessed using Design of Experiment (DOE) in order to understand their influence on soil quantity transferred on shoes. The Faced Central Composite Design (FCCD) using a quadratic model was found to be highly significant, thus they could be adequately used to model and to interpret the amount of soil recovered from one shoe. These designs demonstrate that the characteristics of the donor (soil type and soil humidity), as well as a combination of these two factors have a very significant impact on the soil transfer. The characteristics of the receptor (shoe profile, shoe size and walker's weight) also have an impact on the transfer but to a lesser extent. Globally, this research provides valuable information for the forensic scientist both in investigative mode: evaluation of the soil quantity possibly transferred on shoes, and in the evaluative steps: is the quantity of soil found on the suspect shoes in accordance to the proposition/scenario given by the prosecution and the defence?

Classification of urban soils for forensic purposes using supervised self‐organizing maps

“…Because, according to the Police Department, the soil from these parks was not analyzed for forensic purposes in the period 2016-2019, 3 years later (in the autumn of 2019), additional 12 samples were collected primarily (1) to validate our models with new data, but also (2) to examine the influence of the seasonal changes and the weather on the composition of the soil in these parks. These samples were taken from the same parks by not from the same exact positions.…”

“…The soil is slowly changing material due to its exposure to the weather, the seasonal changes and biological processes. This effect on the composition of the soils is important due to the fact that (1) by court order the forensic evidence could be reexamined or (2) in the cases where the crime investigated has happened few years earlier. In order to examine how our models will perform on soils, taken from the same location, but 3 years later, 12 additional samples were collected from three of the five locations.…”

“…In criminal activities, the soil can be transferred from a crime scene to items linked with a perpetrator (e.g., shoes, cars, or tools). In this process, the amount of soil transferred is influenced by five chosen parameters, namely, the shoe profile, shoe size, walker's weight, soil type, and its humidity 1,2 …”

“…In this process, the amount of soil transferred is influenced by five chosen parameters, namely, the shoe profile, shoe size, walker's weight, soil type, and its humidity. 1,2 The soil has complex and unique properties that are influenced by its chemical and physical composition. Namely, the soil is a heterogynous mixture that contains minerals, organic matter, microorganisms, air, and water.…”

A fresh scientific look at transfer and persistence: From a materials science and tribology perspective

“…explosive [33][34][35] and gunshot residues (GSR) [36][37][38][39][40][41], and soil [42][43][44][45][46], as well as other less commonly encountered traces including glitter [47], fragrances [48][49][50], lipsticks [51], petrol [52], and polyurethane foam [53]. While valuable, such research tends to be very material-dependent, introducing specific parameters and interpretations that may have actually impeded the recognition of underlying foundational factors that could apply to most material types.…”