Tracking the Route Walked by Missing Persons and Fugitives: A Geoforensics Casework (Italy)

Abstract

Criminal investigations aiming to track the route walked by missing persons and fugitives (MPFs) usually involve intelligence analysts, military planners, experts in mobile forensics, traditional investigative methods, and sniffer dog handlers. Nonetheless, when MPFs are devoid of any technological device and move in uninhabited rural areas devoid of tele cameras and densely covered by vegetation, tracking the route walked by MPFs may be a much more arduous task. In the XVIII century, the expert Georg Popp was able to link a homicide suspect to a sequence of different sites of criminal interest, located in the countryside, by studying the stains of soils found on the footwear and trousers of the suspect. In such complex cases, a very efficient approach for tracking the route walked by MPFs may consist of comparing the geological traces found on the MPFs and their belongings with soils exposed in the event scenes. In particular, the search for peculiar or rare particles and aggregates may strengthen the weight of the geological forensic evidence comparisons. A match of mineralogical, textural, and organic matter data may demonstrate the provenance of the traces from the soil of a specific site, thereby linking the MPFs to the scene of events. Based on the above, the present paper reports geological determinations accomplished for a “mediatic” casework. The results allowed a general high degree of compatibility among traces collected on the MPFs and on the soil from the scene of events to be ascertained. The most significant positive matches, based on the finding of ten peculiar and rare particles and assemblages, allowed the reconstruction of a route about 1.1 km long, as the crow flies, on the event site. Although this procedure was extremely time consuming and available only in a backwards reconstruction linked to the MPFs’ findings, it was of uttermost importance in strengthening the inferences proposed, and for which other methods could not provide any information.

1. Introduction

Since the 11 September 2001 attacks and the Global War on Terror, the organizational structures and procedures devoted to the search for persons of national and international interest assumed an important role in global counterterrorism strategies [1,2]. In particular, criminal investigations aiming to track routes walked by missing persons and fugitives (MPFs) in urban and rural territory usually involve intelligence analysts (IMINT—Imagery Intelligence, OSINT—Open Source Intelligence, etc.), military planners, experts in mobile forensics sniffer, dog handlers, and traditional investigative methods [1,3]. Nonetheless, to track the route traversed by the MPFs may be a very arduous task when the MPFs do not carry mobiles, GPS, or any other technological devices, and they move in uninhabited rural areas of the countryside devoid of security or private tele cameras and covered by dense vegetation. In such peculiar circumstances, as demonstrated since the end of the XVIII and beginning of the XIX centuries [4,5,6], the mapping of the paths walked by the actors of crimes can be realized thanks to comparative analyses based on geological and soil forensic evidence collected on the crime actors and the scenes of the events, respectively. In Germany, an expert, Georg Popp, solved different homicide cases using micro-stratigraphy. Procedures of micro-stratigraphic sampling and analyses of the footwear of a homicide suspect may provide a small vertical-scale record testifying the lateral movement of the suspect on different sites of the crime scene, due to the contact of the footwear on the topsoil and the related soil/sediment transfer to the suspect [4].

Nowadays, once the MPFs are found, dead or alive, a very efficient backwards criminalistic approach may consist of comparing both the geological traces and micro-traces found on the MPFs’ belongings (unknown samples, i.e., of unknown provenance) with soils/sediments and plants exposed in the sites of finding, last sighting, alibi, and investigative interest (known samples, i.e., field samples of known provenance). A match of the comparative analysis data may demonstrate the provenance of the unknown traces from a site showing analogous microenvironmental characteristics [7].

Despite the positive results and practical aspects of such investigations, in Italy, forensic geology currently still represents a minor discipline of the forensic sciences panorama. For this reason, this paper is addressed especially to prosecutors, police forces, and politicians in order to demonstrate that this criminalistic discipline should be developed in the future.

With this in mind, the present research reports the scientific method and main results of geological comparative analyses requested by the judicial authority to solve a “mediatic” forensic casework that occurred in the Italian countryside a few years ago. Geological data allowed the tracking of the route walked by the two MPFs, revealing very useful information for the consequent criminological and criminalistic implications.

2. Geoforensics

Forensic sciences, based on a holistic approach, uses different multi-disciplinary and transdisciplinary disciplines, such as criminology and criminalistics (forensic medicine, forensic pathology, dentistry, toxicology, serology, anthropology, archaeology, entomology, physics, biology, chemistry, computer science, geology, and botany, among many others) [8,9]. The main biological, physical, chemical, geological, and botanical forensic evidence (i.e., samples related to the actor of the crime and of investigative interest to be submitted to trial) may be individual or belong to a class. The individual forensic evidence may allow the identification of a person with an elevated degree of certitude (e.g., DNA and fingerprints). The class forensic evidence may allow the identification of a group of persons/objects (i.e., blood groups, glass, fibers, paper, plastics, hairs paints, soils, etc.) [2].

Geoforensics (or forensic geology) is a discipline that is 150 years old, and probably originated during the Roman empire period. In the historical criminological/criminalistic scenario, a few examples of worldwide mediatic serious crimes solved by forensic geologists may be related to cases of kidnapping and homicide of victims, as in the case of the honorable Aldo Moro (1978, Italy) [9,10] or the agent of the DEA (Drug Enforcement Administration) Enrique Camarena Salazar (1985, Mexico) [4], or cases of searches for MPFs, such as the terrorist Osama bin Laden (2001, Afghanistan) [11].

Forensic geology applies principles, methods, and techniques of the earth sciences to solve criminal cases [12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29]. These latter mostly concern crimes against human beings (homicides, kidnappings, sexual violence, robbery), animals, property (burglary, damaging), the environment (environmental disaster or pollution) [30,31,32,33,34,35,36,37], and counterterrorism [11]. In particular, in serious crimes that occur outdoors in the countryside, such as homicides or kidnappings, it is highly probable that useful info-investigative diversified data may be obtained, especially in investigations that aim to define the following:

• Their pre—mortem presence on the scene.
• Their walking route on the site.
• The possible transfer of the victim’s corpse in secondary crime scenes.
• The modality of the victim’s death.

The stratigraphical approach may be of paramount importance when micro-stratigraphic sequences on belongings of the suspects are recognized and sub-sampled. Several sequential layers of different soils/sediments may be recognized in the footwear or clothing of the actors of crimes. In particular, the grooves present on the footwear’s soles may gather and preserve soil/sediment traces transferred from the top soil to the shoe, providing an ordered set of micro-layers where the oldest (the first one to transfer) is in contact with the sole and the youngest (the last to transfer) is the more external [2]. In such circumstances, the stratigraphy principle of superposition will assist in the reconstruction of the timing of the events [2].

The main forensic analyses and activities devoted to criminal cases may involve the following:

• Comparative analyses and provenance studies, based on mineralogical, petrographic, sedimentological, paleontological, and geochemical investigations [38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54]. Forensic comparisons between two or multiple samples of geological and soil traces and micro-traces are aimed to ascertain whether they originated from different sources [51]. When specimens are found to be indistinguishable, the possibility that a single source is the provenance area of the samples cannot be excluded [51]. Such investigations may allow the actors of a crime (suspect and victim of a homicide) to be linked to the crime scene or the scene of events.
• Mineralogical, geochemical, and paleontological analyses.
  These studies, also based on comparative analyses of geomaterials (such as gemstones, fossils, artworks) may allow the authenticity and provenance to be ascertained, as in the cases of frauds, product tampering, art crime, conflict minerals, and fossil fakes [51,55,56,57,58,59].
• Remote sensing, geological, geochemical activities, together with geophysical shallow prospecting and applied geology investigations.
  These investigations [60,61,62,63,64,65,66,67,68,69,70,71,72,73], also based on comparative analyses, may allow the characterization of the environmental matrices (soil and water) and the related underground features in cases of environmental crimes. In particular, remote sensing surveys are carried out to locate MPFs, dens of terrorists, or, in general, illicit activities, using photos, ortho imaging, videos, and photograms, in visible, ultraviolet, and infrared spectra, and elaborated in GIS systems [61,62,64,65,66,67,68,69,70]. Such investigations may also be applied to depict and search for shallow clandestine gravesites and concealments [74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92].

The main comparative analytical methods are used to characterize composition, textures, and structures of the inorganic, organic, and anthropogenic components of the geological and soil forensic evidence (

Table 1. Main methods and techniques usually applied for comparative analyses of geological forensic evidence in a laboratory. * Instruments also portable in the field.

Matrices	Methods and Techniques	Analyzed Characteristics
Geological samples	Spectrophotometers/Munsell charts/computational methods	Color
Geological samples	Mechanical sieve/Laser diffraction particle size analyzer/Coulter counter/particle size analyzer through automated microscopy and image analysis for measuring particle size and particle shape	Texture (grain size, morphology)
Geological samples	Optical microscopy (OM) using a stereo microscope *, in transmitted and reflected light, with tele camera and workstation for image analyses	Texture/Structure
Geological samples	Optical microscopy (OM) using a polarizing microscope, in transmitted and reflected light, with tele camera and workstation for image analyses	Mineral composition/Texture/Structure
Geological samples	Powder X-ray diffractometry (PXRD)	Mineral composition
Geological samples	Scanning electron microscopy with energy dispersion system (SEM—EDS)/quantitative evaluation of minerals via scanning electron microscopy (QUEMSCAN)	Composition/Texture/ Structure
Geological samples	Scanning electron microscopy (SEM)	Composition/Morphology
Geological samples	X-ray fluorescence (XRF) *	Elemental qualitative determination
Geological samples	µ—RAMAN spectroscopy */FTIR spectroscopy	Molecular qualitative determination
Geological samples	Inductively coupled plasma-mass spectrometry (ICP—MS)/inductively coupled plasma—optical emission spectroscopy (ICP—OES)/instrumental neutron activation analysis (INAA)	Elemental quantitative determination

).

Forensic soils (and sediments) are usually composed of three different components:

The inorganic component (minerals and micro- to nano-fossils).

• The organic component (vegetal and animal remains).
• The anthropogenic component (manufactured materials such as glass, plastic, paper, and brick fragments).

The main parameters and characteristics investigated in the inorganic component may be synthesized as follows (Table 1):

• Color.
• Particle size.
• Structure and texture.
• Fossil content.
• Mineralogy.
• Chemical and chemical–physical composition.

The organic component, vegetal and animal, may be very abundant and important in the sample. Once identified, it must be separated by the geologist and submitted to the specialistic analyses of forensic botanists and entomologists, respectively. In particular, the finding of plant remains such as seeds, thorns, leaves, and pollens or their associations have been demonstrated to be very useful for linking forensic evidence to a specific environment of provenance and for dating the period of transferring the trace [10,93,94,95,96,97,98,99]. New advances in forensic biology on the vegetal DNA identification may demonstrate the transfer of a specific plant DNA to an actor of crime. Such a multi-disciplinary scientific approach on inorganic and organic forensic evidence based on standardized protocols [100] and procedures reported in the international scientific literature may provide very useful data, especially in crime scenes that occur in the countryside.

The study of the geological forensic evidence may assist in establishing the degree of similarity among samples to associate or exclude a suspect to/from the victim and crime scene, by comparing the characteristics of the unknown samples with those of the known samples (field sample). On the basis of the above, it is evident that ascertaining the compatibility or similarity among geological and soil traces and micro-traces of unknown provenance (unknown sample), and soils and sediments of known provenance (known samples or field samples), may assume a fundamental role in the geoforensics investigations. Nonetheless, a simple compatibility among forensic specimens may not be decisive if not supported by strong geological, biological, physical, and chemical forensic evidence. As a matter of fact, in contrast to individual characteristics (DNA, fingerprints), the provided geological and soil forensic evidence having class characteristics [9] needs to be carefully investigated to obtain assessable data. To achieve a high probatory value of the forensic evidence presented to the court, the main task should be to gain the highest number of geological characteristics and peculiar particles [4] to compare.

If the wide range of compared characteristics provides forensic evidence that there is a match, or not, among compared forensic specimens, it is possible to link the actors of a crime to the criminal act, or, with a high level of probability exclude them from it, respectively, by ascertaining that the compared specimens possess features analogous to those of a specific microenvironment from which these may derive [19,23].

3. Criminal Casework

Although the presented criminal proceeding was archived, the author preferred to deal with the data and inferences described below by presenting MPFs/victims, samples, dates, sites, and infrastructures anonymously.

A few years ago, an Italian locality of the countryside was the sad scenario of a criminal case of presumed kidnapping, which was concluded after sometime with the finding of the human remains of two subjects. One day, the two persons left their home, and after a car accident, they quickly abandoned their car and belongings, departing the site. They disappeared into thin air, and nobody saw them in the surrounding areas. A few days after their disappearance, the two MPFs were found lifeless in two separate sites not too far from the site of the car accident (Figure 1). Victim 1 was found about 1.1 km away, as the crow flies, from the place of the last sighting (Figure 1), under an element of infrastructure, a few meters away. One shoe was found on the ground near the corpse, the other one in suspension attached to a shrub. The remains of victim 2 were approximately located at 0.5 km from the site of the car accident, halfway between it and the place where victim 1 was found (Figure 1). The body was found skeletonized and bones were found dispersed in an area (wide about 800 m²) of the dense Mediterranean maquis.

The shoes of victim 2 were found a few tens of meters from the remains, at a higher altitude.

The judicial authority instigated an impressive investigation, covering a wide spectrum of traditional and scientific investigations, inter- and trans-disciplinary, employing disciplines usually used for the 360° characterization of serious crimes that happen outdoors in the countryside, such as legal medicine, forensic pathology, odontology, entomology, toxicology, veterinary, psychiatry, engineering, computer science, physics, geology, and botany.

In particular, considering that the two MPFs were not carrying any mobile, GPS, or electronical devise, the judicial authority gave to the author the task of ascertaining the active pre—mortem presence of the two MPFs at the event site and to reconstruct the route walked by them, if possible.

4. Materials and Methods

Although geological traces are mostly provided having class characteristics, a sort of “fingerprint” of the specimens [101] may be identified by means of a careful examination of both peculiar and rare grains [4], minerals, composition, textural features, and peculiar assemblages of minerals and vegetal remains studied in both the unknown and known specimens to be compared. A clever expert should be able to carry out comparative analyses based on a wide range of parameters and characteristics.

With this in mind, the comparative analyses were performed tracing the “fingerprints” of both geological trace forensic evidence (related to the two MPFs and their belongings) and soils (related to the event scene and localities of investigative interest).

Geological trace forensic evidence (unknown samples) was sampled by searching for traces under a magnifying glass (10×, 20×, 30×) on the two cadavers during the autopsy, and successively on their belongings and skeletal remains using a stereomicroscope in a laboratory of forensic geology. Special attention was devoted to the footwear, which were in strict contact with the topsoil during the movement of the MPFs. Such contact, as stated by the Locard exchange principle, may allow an easy transfer of inorganic and organic (plant and small animal remains) particles from the topsoil to the footwear, linking in such a way the subject to a specific site [102,103].

The shoes of MPF 1 were found to be very dirty and scratched (Figure 2A,B), very rich in vegetal material (mostly seeds and thorns inside the shoes and fixed on the soles and laces, Figure 2C), and with inorganic traces (Figure 2C).

MPF 2’s shoes were intact, in a pair, and with inorganic and vegetal traces (mostly thorns fixed on the soles).

Multiple pieces of soil forensic evidence (known specimens) were collected on the sites where the human remains were found (known samples), and the localities were trampled by the victims with the same footwear in the days immediately before the disappearance event, for exclusion purposes. With the same aim, footwear of the two MPFs were also sized to characterize the usual type of traces present.

A few hundreds samples were collected overall.

Multiple pieces of geological trace and soil forensic evidence were first analyzed under a stereomicroscope [4], as they were found. Field samples were treated, mechanically sieved, and separated. Particle size analysis (PSA) was carried out on field samples using the laser diffraction technique. Trace samples, due to their limited amount, were “virtually” separated on the base of the diameter by means of image analyses, after having taken microphotographs under a stereomicroscope. Different sub-samples on the basis of the grain size were obtained.

Optical analyses under a stereomicroscope and SEM-EDS, both provided at a workstation, were conducted to investigate the following main parameters and characteristics: color, coating, shape, habitus, luster, particle size, texture, fossil content, and mineralogy. Stubs of the samples with selected particles were prepared for the SEM-EDS forensic characterization, in order to investigate both morphological features at higher magnification and composition. Smear slides of the specimens were observed under a petrographic microscope for an expeditious characterization of mineralogy and fossil content. The different parameters and features were quantitatively characterized by counting each particle of the specimens (at least 100 particles for the sample) for the most widespread grain sizes. Particle morphometry was determined by means of image analysis software. The Riley sphericity (√$\frac{Di}{Dc}$) (Di: the diameter of the largest inscribed circle, Dc: the diameter of the smallest circumscribing circle) was applied for the two-dimensional sphericity measurement. The roundness was determined by means of comparative charts.

The protocols used for geological analyses conformed with those in Bourguignon et al. (2019) [100] and the international literature.

Botanical forensic evidence was collected by the author from the victims and their belongings, or separated from the geological trace forensic evidence. Vegetal elements were sampled on the plants growing on the sites of the events and other sites of investigative interest or separated from the soil forensic evidence. Morphological determinations on plants (including algae) were accomplished under a microscope by a team of experts in systematic botany.

Particle size analyses and separations were performed by using the following:

• Mechanical sieve (AS 200 control model, Retsch, Düsseldorf, Germany) with sieves (meshes of 2000 µ, 1000 µ, 500 µ, 250 µ, 125 µ, 63 µ).
• Laser diffraction granulometer (Mastersizer 2000, Malvern Panalytical Ltd, Malvern, UK) equipped a with wet dispersion unit and workstation (Figure 3A).
• Motorized stereomicroscope equipped with a digital camera and workstation (SteREO Discovery V20, Carl Zeiss AG, Feldbach, Switzerland) (Figure 3B).

Analyses were performed on particles contained in Petri capsules, glass slides, smear slides, and stubs with carbon adhesive using the instruments having the following characteristics:

• Stereomicroscope (Leica MZ 12, magnifications from 8× to 100×, Leica Microsystems, Wetzlar, Germany).
• Motorized stereomicroscope with reflected and transmitted polarized light (Zeiss Stereo Discovery.V20, magnification from 3.8× to 530× with optical zoom) equipped with digital camera and workstation (Carl Zeiss AG, Feldbach, Switzerland).
• Motorized petrographic optical microscope with reflected and transmitted polarized light (Zeiss Imager.M2m model, magnifications from 25× to 500×) equipped with tele camera and workstation (Carl Zeiss AG, Feldbach, Switzerland) (Figure 3B).
• Optical microscope for biological use (Leitz Laborlux 12, magnifications from 40× to 1000×) equipped with 12 MP digital camera (Leitz GmbH & Co KG, Stuttgart, Germany).
• SEM operating in low vacuum, chamber pressure of 50 Pa at 20.00 kV e (FEI QUANTA FEG 450 model) equipped with an Energy Dispersive System (X-ray analyzer, SEM-EDS, FEI, Hillsboro, OR, USA) and workstation (AMETEK, Berwyn, PA, USA) (Figure 3C).

5. Results on the Comparative Analyses

5.1. Geological Forensic Evidence

Samples were found to comprise sandy to silty hyaline siliciclastic grains mainly composed of mono-mineral grains/clasts of quartz with different intensity yellow to orange Fe-coatings, minor opaque yellow ocher lithoclasts of quartzarenites, and microfossils (benthic and planktonic foraminifera).

Mineralogical, petrographic, and sedimentological examinations of the geological trace and soil forensic evidence revealed that these were mainly composed of an analogous mineral assemblage. Despite the mineralogical homogeneity, seven main classes of grain typologies were identified on the basis of different mineralogical and textural characteristics and parameters (luster, coating, color, shape, habitus, roundness, and sphericity) examined under a stereo-binocular reflected and transmitted light microscope and SEM-EDS.

The identified grain characteristics and parameters were described for each class. About one thousand medium-fine to very fine sandy grains were analyzed in the unknown samples as well as in the known samples (field samples), in the complex (

Table 2. Characterization of the different types of grains identified in the forensic unknown and known samples of the casework.

Class ID	Description
ID01	Hyaline grains predominantly rounded and triangular in shape with yellow/orange coating, which gives the grains a hyaline appearance with more or less marked yellow/orange “spots” up to straw yellow/orange/reddish.
ID02	Rounded hyaline grains with evidence of the original crystalline habitus with yellow/orange coating, which gives the grains a hyaline appearance with more or less marked yellow/orange “spots” up to straw yellow/orange/reddish with minor percentage of sub-angular clasts.
ID03	Predominantly rounded and spherical hyaline grains without coating.
ID04	Hyaline grains with rounded tabular crystalline habitus and without coating.
ID05	Rare hyaline grains of smoky gray color and without coating.
ID06	Rounded and spherical hyaline clasts with yellow/orange coating, which gives the clasts a hyaline appearance with more or less marked yellow/orange “spots” up to straw yellow/orange/reddish with a smaller percentage of sub-angular and lamellar grains.
ID07	Opaque grains mainly yellow ocher and fossil forms (mainly benthic foraminifera) with a smaller percentage of opaque brown or light grains.

, Figure 4).

Grains appeared to be mostly rounded with a minor percentage of sub-angular clasts, whereas the Riley sphericity was found to be equal to 0.8 in both the unknown and known samples (field samples).

Additional comparisons, accomplished in order to exclude possible previous traces in the victims’ questioned samples, related to their staying with the same footwear in the sites visited in the days immediately before the tragic event. These allowed the absence to be ascertained of particles composed of mono- and polymineral assemblages of metamorphic rocks typical of the soils collected in these other locations of investigative interest.

Two (250–125 µ, 125–63 µ) and three (250–125 µ, 125–63 µ, <63 µ) grain sizes were identified as the most representative ones of both the unknown and known samples. The distribution of the quantitative data related to the seven class characteristics of the unknown and known samples, reported for both the 250–125 µ and the 125–63 µ grain sizes, showed optimal overlaps and trends (Figure 5). In particular, three main types of grains were prevalent in both unknown and known samples. These were, in order of abundance (Table 2, Figure 5):

i.

ID06—Rounded and spherical hyaline clasts with yellow/orange coating with a percentage of sub-angular and lamellar grains.

ii.

ID02—Rounded hyaline grains with evidence of the original crystalline habitus with yellow/orange coating.

iii.

ID03—Rounded and spherical hyaline grains without coating.

5.2. Botanical Forensic Evidence

Forensic botany was applied for the present casework in order to corroborate the forensic geology investigations. The amount of the vegetal material prevailed on the inorganic grains. The vegetal fraction separated from the geological traces related to the unknown samples from the MPFs and their belongings, and observed via stereomicroscopy, microscopy, and SEM-EDS, was found to be composed of plant fragments or entire elements of branches, twigs, leaves, thorns, capsules, fruits, seeds, pollen, herbaceous fragments, wood, vegetable debris, decomposing organic material (humus), and algae (including diatoms).

The main 12 species of remnants of traces of the identified terrestrial plants were as follows [98]:

• Erica arborea (leaves, capsules, seeds).
• Quercus suber (leaves, flowers, seeds).
• Olea europaea (leaves, seeds).
• Cistus monspeliensis (leaves, seeds, capsules, etc.).
• Pistacia lentiscus (leaves, seeds).
• Myrtus communis (leaves, seeds).
• Cytisus infestus (branches, legume, thorns).
• Smilax aspera (leaves, thorns).
• Rosa sempervirens (thorns).
• Rubus ulmifolius (thorns).
• Rosacea Amygdaloidea (thorns).
• Cynara cardunculus (thorns).

Peculiar particles were considered the thorns and seeds, which were the most abundant vegetal component sampled on bodies, clothing, and footwears of both MPFs.

Over 522 seeds of Erica arborea and 81 thorns ascribable to Rosa sempervirens, Rubus ulmifolius, Rosacea amygdaloidea, Cynara cardunculus, Cytisus infestus, and Smilax aspera were found in the shoes of victim 1, mostly inside the shoes and planted on the soles, respectively. Another peculiar material was represented by an aggregate made up of remnants of freshwater algae found in the sole of victim 1’s footwear [98].

Only 16 thorns ascribable to Rosa sempervirens or Rubus ulmifolius, Cynara cardunculus, Cytisus infestus, and Smilax aspera were found on the soles of the shoes of victim 2. No traces of algae were found, except a unique diatom [97,98].

The same 12 species of terrestrial plants reported above were also found in the vegetation present at the sites of the events and in the vegetal component of the soils collected from this area.

On the basis of the above, four main macro-areas with different botanical characteristics were distinguished during remote sensing and field work. The identified macro-areas were as follows [98]:

• Shrub formation with Mediterranean maquis (prevailing macro area).
• Area inside the highway perimeter.
• Meadow area with anthropic pressure from pasture with some puddles of freshwater with algae.
• Tree formation dominated by Sughera (Quercus suber L.), with a circumscribed zone showing abundant concentration of Erica arborea shrub wood and soils rich in fresh to decomposed seeds of Erica arborea (about 6000 seeds of Erica arborea were examined and counted in the soils).

5.3. Tracking the Route Walked by the Two MPFs

During investigations, great attention was also devoted to the specific search for rare or peculiar particles or assemblages of inorganic and vegetal origin. This examination allowed the unknown samples collected on the victim belongings to be recognized:

• Rare particles of calcite and dolomite.
• Peculiar compositions of clay minerals rich in calcium phosphate.
• Peculiar assemblages of different classes of mineral grains.
• Vegetal remains of mm-sized thorns of Cynara cardunculus and Rosa sempervirens, seeds of Erica arborea, and assemblages of algae.

The same rare and peculiar materials were also recognized in some specific sites of the scene of events, as specified in the following. Geobotanic data on the unknown samples were found to be typical of microenvironments very similar to those identified at the scene of events. These results were of paramount importance in allowing investigators and the judicial authority to link the MPFs to specific sites of the scene of events and in tracking the routes of both the MPFs, which were obtained from nine specific microenvironments recognized at the scene of events.

Figure 6 and

Table 3. Sites selected for linking MPFs to the event sites and reconstructing the route walked by them.

MPFs/Victims	Acronyms	Typology of Sites for Linking MPFs to Event Site
MPF 1–MPF 2	CA	Car accident site (Route start point)
MPF 1	M1	Match point (inorganic traces)
MPF 1–MPF 2	M2	Match linear belt (organic traces)
MPF 1–MPF 2	E1	Exit (rudimental wood gate)
MPF 1	M3	Match point (organic traces)
MPF 1–MPF 2	M4	Match point (inorganic traces)
MPF 1–MPF 2	M5	Match point (inorganic traces)
MPF 1–MPF 2	E2	Exit (rudimental wood gate)
MPF 2	M6	Match point (inorganic traces)
MPF 1–MPF 2	E3	Entry (hole in the barber wire perimeter)
MPF 1	M7	Match linear belt (organic traces)
MPF 1	M8	Match point (inorganic traces)
Victim 2	F2	Finding site of skeletonized human remains
MPF 1	E4	Exit (hole in the barber wire perimeter)
MPF 1	M9	Match point (organic traces)
Victim 1	F1	Finding site of human remains (Route end point)

illustrate the sequence and distribution of the match points and match linear belts (M), from which the path was delineated by means of interpolation of matching sites and four exit/entry points (E1–4), recognized in the event scene during field work, starting from the site of the car accident site (CA). The locations of the two different sites at which the human remains were found (F1 and F2) were also reported.

5.3.1. Car Accident (Table 3, Figure 6)

The two subjects abandoned the site of the car accident, which occurred inside a tunnel of the highway.

5.3.2. Match Point 1 (M1) (Table 3, Figure 6)

Inorganic micro-traces (calcite) from MPF 1’s ring.

These micro-traces were comparable with the calcareous composition of the top of a ~1 m high perimeter wall delimiting the lateral gate of the highway (Figure 7).

5.3.3. Exit (E1) (Table 3, Figure 6)

The two MPFs passed through a rudimentary wood gate delimiting the area surrounding the highway tunnels.

5.3.4. Match Linear Belt 2 (M2) (Table 3, Figure 6)

Organic traces (thorns of Cynara cardunculus) from MPF 1’s sock and MPF 2’s shoes.

This forensic evidence was comparable with some thorny plants growing on an uncultivated field in the meadow area with anthropic pressure from pasture (Figure 8).

5.3.5. Match Point 3 (M3) (Table 3, Figure 6)

Organic traces (algae) from MPF 1’s shoes.

These were comparable with algae present in fresh water of a muddy puddle (Figure 9).

5.3.6. Match Point 4 (M4) (Table 3, Figure 6)

Inorganic micro-traces of P-rich clays from MPFs’ shoes.

These were comparable with wet soil present on the muddy puddle reported above (Figure 10).

5.3.7. Match Point 5 (M5) (Table 3, Figure 6)

Inorganic traces from MPF 2’s shoes.

This particle assemblage was comparable with the sandy and silty soil present in a specific site of an uncultivated field in the meadow area with anthropic pressure from pasture (Figure 11).

5.3.8. Exit Point (E2) (Table 3, Figure 6)

The two MPFs passed through a rudimentary wood gate delimiting an uncultivated field in the meadow area with anthropic pressure from pasture.

5.3.9. Match Point 6 (M6) (Table 3, Figure 6)

Inorganic traces (dolomite) from MPF 2’s shoes (Figure 12A).

These were comparable with clasts of pinkish dolostones artificially reported on a dirt road present on an uncultivated field, near a wood rudimentary gate (Figure 12B).

5.3.10. Entry Point (E3) (Table 3, Figure 6)

The two MPFs passed through a passage in the barbed wire delimiting the Sughera wood with Erica arborea plants, and entered this area.

5.3.11. Match Linear Belt 7 (M7) (Table 3, Figure 6)

Organic traces (Erica arborea seeds) from MPF 1’s shoes (Figure 13) and socks.

The freshness state of the Erica arborea seeds in MPF 1’s shoes (Figure 13A) was comparable with that of seeds present in the soil in the wood with Sughera (Quercus suber L.) and associated with Erica arborea shrubs, as cited above (Figure 13).

5.3.12. Match Point 8 (M8) (Table 3, Figure 6)

Inorganic traces from MPF 1’s shoes.

This particle assemblage was comparable with the sandy and silty soil present in the area of the wood with Sughera (Quercus suber L.) and Erica arborea shrubs (Figure 14).

5.3.13. Finding Site (F2) (Table 3, Figure 6)

The skeletonized human remains of victim 2 were found distributed in an articulated area of the dense Mediterranean maquis.

5.3.14. Exit (E4) (Table 3, Figure 6)

MPF 1 passed through a passage in the barbed wire delimiting the Sughera wood with Erica arborea plants, thus abandoning this area.

5.3.15. Match Point 9 (M9) (Table 3, Figure 6)

Organic traces (Rosa sempervirens thorns) from MPF 1’s shoes, socks, and clothing.

These traces were comparable with the thorns of the climbing Rosa sempervirens plants growing on the infrastructure in proximity of the site at which the corpse was found (Figure 15).

5.3.16. Finding Site (F1) (Table 3, Figure 6)

The body of MPF 1 was found under an element if infrastructure in a prone position.

6. Discussion and Conclusions

Finally, it seems appropriate in this discussion to underline some considerations related to the criminal investigations.

In the USA, the geological evidence in a trial for the kidnapping, sexual violence, and murder of a 9-year-old girl led the jury and the judge to condemn the criminal, with a sentence of the death penalty [50]. In Italy, although the criminal law is different, it cannot be considered a minor responsibility to limit the personal liberty of a suspect. A proper background knowledge in forensic sciences is an opportune requirement that each expert should take care to have before accepting any forensic charge. The knowledge of base concepts in both criminalistics (crime scene analysis and legal medicine) and criminology (forensic psychiatry and psychology, criminal law, investigations, and intelligence) is of paramount importance in forensics in order to have a complete setting of the case and to limit possible procedural errors. The familiarity in these matters may have an influence by contributing to the positive results of investigations.

During each one of the judicial inspections made at the crime scenes or event scenes, the expert may benefit from forensic sciences expertise. The use of the investigative empathy and the knowledge of the psychological background of the victims or suspects may help ensure that no hypotheses are ignored. In cases such as that presented here, a central aspect of field work is to walk, several times, every possible path at the event sites. To quantify the physical efforts and difficulties involved in crossing shrubs, infrastructures, and narrow passages; to walk with the same models of shoes and clothing of the victims; to search for all possible exit–entry passages; to study the slope, meteorology, and ephemeris conditions at the time of the event; and, last but not least, to see the scene of events with the eyes of the victims, may be actions that are fundamental to directing investigations, discarding certain hypotheses, and strengthening the obtained results.

On the other hand, the multi-disciplinary approach presented here allowed experts in geology and botany to work in a team in the field, and, at different times or jointly, on the same samples in the same laboratory. This work organization, although analyses were particularly time consuming, allowed the amount of time required for the conclusion of the forensic investigations and the submission of the report to the judicial authority to be significantly reduced.

The wide spectrum of mineralogical, morphological, morphoscopic, textural, and geobotanic determinations accomplished for the present criminal casework allowed a general high degree of compatibility to be ascertained among traces sampled on the MPFs and field samples collected at the scene of events, and the exclusion of possible previous traces related to their staying with the same footwear at other sites in the days immediately before the tragic event.

These comparative analyses provided fundamental info-investigative data of paramount importance for establishing the active pre–mortem presence of the MPFs at the scene, and to deal with a criminal case for which other methods were not very useful and inapplicable. No–one saw the MPFs walking in the countryside, the MPFs were not carrying any mobiles, GPS, or technological devices, and no tele cameras were at the scene.

The most significant positive matches, based on the finding of ten peculiar and rare particles and assemblages, allowed the reconstruction of a very detailed walking path, of about 1.1 km long, as the crow flies, that was carried out by the two MPFs on the event site.

As a matter of fact, the finding of ten different points and linear belts having a positive match, from 1 (near the car accident site) to 9 (the site at which victim 1 was found), allowed the reconstruction and tracking of the route walked by the two MPFs in the hours immediately preceding their death (Table 3, Figure 6). The inferences obtained by data interpretations were very useful for the judicial system. A few criminological and criminalistic inferences based on the investigations, carried out in the laboratory and the field, allowed us to hypothesize that:

• After the car accident (CA, Figure 6) on the highway, the two subjects abandoned their vehicle and walked out of the tunnel, reaching a lateral gate beside the highway. They presumably ran away to hide themselves in the countryside.
• The transfer of calcite particles from the perimeter wall of the highway to the ring (M1, Figure 6) happened when MPF 1 passed on wall, touching it with their hands, in order to reach the raised ground behind the highway.
• A first exit (E1, Figure 6) allowed the two MPFs to walk off the highway.
• The transfer of thorns of Cynara cardunculus to MPF 1’s sock and MPF 2’s shoes (M2, Figure 6) occurred when the subjects walked on these thorny plants distributed in a linear belt.
• The transfer of algae from a freshwater puddle to the soles of MPF 1’s shoes (M3, Figure 6) happened when the subject walked in this specific puddle.
• The transfer of P-rich clay from wet soil to the soles of the two MPF’s shoes (M4) occurred when they walked in the wet area.
• The transfer of the sandy and silty soil from a specific site to MPF 2’s shoes (M5, Figure 6) happened when the MPF walked in this locality.
• A second exit (E2, Figure 6) allowed the two MPFs to walk from the meadow area, which was subject to anthropic pressure from pasture.
• The transfer of dolomite clasts to MPF 2’s shoes from a dirt road (M6, Figure 6), in front of E2, occurred when the victim walked on this road.
• A third passage (E3, Figure 6) allowed the MPFs to enter a Sughera wood with Erica arborea plants. This locality was covered and isolated, and suitable for hiding effectively.
• The transfer of over 522 seeds of Erica arborea from plants and soils present in the wood to the internal parts of shoes and socks of MPF 1 occurred when the victim walked in this area (N7, Figure 6). It may be presumed that the transfer of the seeds occurred when the thick Erica arborea seed-rich soil, and seeds that had fallen from the Erica arborea shrubs due to the impact of the body with them, filled the internal parts of the shoes.
• The transfer of a peculiar mineral particle assemblage to MPF 1’s shoes (M8, Figure 6) happened when the MPF 1 passed through this area.
• This site (M8) was very close to the site (F2, Figure 6) at which the skeletonized human remains of victim 2 were found.
• A fourth passage (E4, Figure 6) allowed MPF 1 to leave the woody area and reach a dirt road.
• The transfer of Rosa sempervirens thorns from the infrastructure to MPF 1’s shoes, socks, and clothing (M9 in Figure 6) presumably occurred when the subject climbed on this structure.
• The prone position of MPF 1’s body at the site at which it was found (F1, Figure 6), its distance from the infrastructure, as well as its relationships with the plants present on the ground unequivocally supported the reconstruction of the manner of death of MPF 1, for causation, as ascertained by the medico legal investigations. In particular, some injuries on the body could be due to the dynamic impact of the body that occurred on the plants growing on the ground.

In synthesis, geobotanic investigations allowed the following to be established:

• Both MPFs actively interacted with the microenvironments recognized at the scene of events in the match sites M1–M9 (Figure 6), as requested by the judicial authority.
• Both MPFs actively walked at the scene of events along a specific route in areas with different degrees of vegetation density and difficulty of passing through (Figure 6).
• MPF 2 walked a shorter path than MGF 1; this path was reconstructed from the car accident site (CA, Figure 6), to the dirty path with detritus of dolostones (M6, Figure 6). It may be hypothesized that MPF 2 was carried out in MPF 1’s arms in the Sughera woody area that contained Erica arborea, from the surrounding of the M6 site to the M8 site, i.e., in an area immediately next to the site at which victim 2 was found (F2, Figure 6). This inference was consequent to the fact that no seeds of Erica arborea were found in the footwear of MPF 2 (notwithstanding adhesive material in the shoes), whereas hundreds of seeds of Erica arborea were found in the socks and footwear of MPF 1.
• MPF 1 walked a longer path than MPF 2 to the site where the body was found (F1, Figure 6).
• MPF 1 actively climbed on the infrastructure (M9, Figure 6).

In conclusion, the peculiar and rare grains, minerals, composition, and textures, together with the peculiar and rare assemblages analyzed in the unknown and known specimens from the victims and the event scene, permitted the identification of a “fingerprint” of most of the examined specimens. Most of these fingerprints were obtained by means of image analysis and the manual counting of grain characteristics. This procedure, although extremely time consuming and relevant only in cases after the finding of the MPF, was of utmost importance in strengthening the reconstructions proposed here. In such a way, investigators were able to provide very strong geological forensic evidence to support criminal investigations. The used approach was of utmost importance in strengthening the proposed inferences, where other methods could not provide any information.

The approach used to track the route walked by the two MPFs could be contrasted with the strategies used to combat the Al-Qaeda terrorism. When a terrorist is captured in the countryside, it may be useful or necessary to trace the route walked by him/her, to search for a terrorist den or a site of investigative interest (burial of firearms, explosives, etc.).

Despite these encouraging and promising results, and the great potential of this method, in Italy forensic geology still represents a minor discipline of the forensic sciences [104]. In the Italian police criminal laboratories, the analysis of geological traces actually rarely occurs, in contrast to the realities of other countries (Federal Bureau of Investigation (FBI) Laboratory of Trace Evidence, Quantico, USA [51,105]; Institute of Criminalistics (ICP), Prague, Czech Republic [106,107]; Australia [50]). Mediatic cases of kidnappings and homicide, as in the case of the Italian honorable Aldo Moro or in the case presented here (whose approach was inspired by the Moro case) were solved using the application of earth science disciplines. At present, after almost half a century, geologists are not involved in the police forces in Italy. This circumstance, anomalous with respect to what occurs in other countries, induces prosecutors, magistrates, and judges to contact geologists, chosen among freelances or academics, to assist them in such criminal investigations [2], thereby imposing a burden on the State’s economic resources.

On the basis of the above, for the next generations of forensic experts in geology, it should be desirable that academics and researchers undertake the following:

• Open a channel of dialogue and technical–scientific discussions with the Ministries of Justice, Defense, and Interior.
• Further implement scientific and didactic initiatives on forensic geology [108,109,110,111,112,113].
• Promote initiatives for introducing the master’s degree in geology in police applications for employing geologists/forensic examiners for the police forensic bureau (Carabinieri, police).
• Develop forensic protocols envisaging all possible technical procedures/operations to be accurately applied at the crime or event scene to preserve forensic evidence made of inorganic and organic materials, and strengthen greater interaction and collaboration between forensic geologists, botanists, and experts in legal medicine directly at the crime scene, in order to arrange all the activities aimed at preserving these traces as far as possible, even during necropsy operations.