INTRODUCTION:

Soil is a mixture of minerals, organic matter and organism that support plant life. It is a dynamic body of natural materials i.e. capable of supporting a vegetative cover¹.

Major soil components:

Soil contains four major components:

· Inorganic materials

· Soil water

· Soil air

· Organic matter

The most important properties include colour, texture, structure, acidity or alkalinity, and capacity to hold and transmit water and air.

TYPES OF SOIL:

1. Clay-it is smooth in texture, dense in nature. It retains water.

2. Silty Soil- It is fertile in nature, retains water, not grainy, not rocky, tiny particles.

3. Loamy Soil- It has a mixture of sand, clay and silt. It has high calcium level. It is granular in texture.

4. Sandy soil- It is granular and gritty in nature.it drains water . does not retain water. Warm and airy

5. Peaty Soil – it is black or dark brown in colour. Has high acidic content. Rich in organicmatter².

Interpretations:

1. Colour

2. Texture

3. Particle Size distribution

4. Density

Soil provides useful information about the link of person to crime scene s because of its nature as the surface of the ground³.

Collection:

The proper collection of known and unknown evidence is important.

There can be problems with limited size and amount, contamination, fragality and stability of the evidence. All the layers should be collected properly.

Dry Soil samples can be put in plastic bags, film canisters, air tight containers.

Wet Soil samples should be collected in paper bags or cloth.

Physical characteristics:

The colour of the soil is affected by moisture content, mineral distribution and location.

Chemical characteristics:

pH, HPLC, IR spectroscopy

Microscope:

Stereo microscope

Polarised light microscope

Seaving method:

Weigh that soil

Put that in top layer having big hole

Succeeded layers has smallest size.

The thin layer of the earth, which is composed of small rock particles and organic matters, living or dead, is termed as soil and is continually under a process of change through time. The nature of soil depends upon the underlying rock known as parent material of the soil. The natural plants, erosion processes and man made activities in the surrounding area also supplement the constituents of soil.

Soil contains microscopic particles called dust. It can be very characteristic of particular places, such as building sites, coal cellers, workshops or flour mills. Similarly, soil near railway tracks, wells, factories, or soils of the fields have surface conditions. Such a contamination of soil with natural or man-made debris, animal remains, organic materials, industrial wastes and fertilizers, etc contribute towards specific local conditions and helps in characterization of soil.

Importance of Soil Samples in Forensic Science:

Forensic soil science is the science or study of soil that involves the application of soil science, especially studies that involve soil morphology, soil mapping (assisted by existing soil maps and spatially held soil data), mineralogy, chemistry, geophysics, biology, and molecular biology to answer legal questions, problems, or hypotheses. Soils mean different things to different people. Some people regard soil as “dirt” or “mud” because it makes them “dirty” when they make contact with it. Soil scientists (pedologists) view soils as being made up of different size mineral particles (sand, silt, and clay) and organic matter. Soils have complex biological, chemical, physical, mineralogical, and hydrological properties that are always changing with tiin^4-7.

Soil as a Powerful Contact Trace:

Theory of Transfer of Soil Materials from one surface to another as a Result of Contact:

The transfer of trace evidence is governed by what has become known as the Locard exchange principle, which states that when two surfaces come into physical contact there is the potential for mutual transfer of material between them. Soil materials are routinely observed on the surfaces of items such as shoes and clothing used as evidence by police, crime scene investigators, and forensic

staff. Primarily, such soil evidence must be recognized on all possible items relating to an investigation. Secondly, the soil evidence must be well documented. Finally, meticulous collection and preservation of soil samples must be maintained so as to preserve the integrity of the soil.

A few questions of general nature which are likely to be of some help to the investigating officers are discussed below, especially with respect to the extent of reliance that can be placed in the results obtained from scientific examinations of soils.

i. Are the two samples of soil A and B collected from the scene of crime and the clothing of suspects essentially the same?

ii. Has the soil taken from the shoes of the suspect (or from the clothes) come from the vicinity of a particular place?

iii. To which specific location does the soil specimen belong?

v. Can a vehicle used as a means of transportation in committing the crime be placed at a certain place on the basis of soil found on it?

Although geographically, soil varies from one area to another, from forensic point of view it varies from spot to spot even in the same area because of the specific localized prevailing conditions such as contamination of soil with nature or man made debris, animal remains, organic materials, industrial waste fertilizers etc. therefore the soil at two different spots would be invariably different and distinguishable.

Soil forensic characterization is primarily performed in the laboratory, it is emphasized that soil analysis typically begins with the sampling and description of three distinct groups of samples, which are categorized as follows: (i) questioned soil samples whose origin is unknown or disputed – often froma suspect or victim (ii) control soil samples whose origin is known – often from sites such as the crime scene.

The role of the forensic soil scientist is to compare materials from these groups of samples and draw conclusions about the origins of the questioned soil samples. Soil materials are being recognized and used in forensic investigations to associate a soil sample taken from an item, such as a victim’s clothing (questioned soil), with a soil from a specific known location such as the crime scene (control soil)^8-11.

Correct sequence for conducting soil forensic investigations:

· Recognition

· Documentation

· Collection

· Preservation

Historical Analysis Methods for Forensic Soil Samples: 1856–1904.

To illustrate how easy it is to characterize soil materials, the following published historical examples demonstrate how soil materials have been characterized using quick morphological and light optical methods to solve crime cases. Further, as documented by Murray and Tedrow “October 1904, a forensic scientist in Frankfurt, Germany named George Popp was asked to examine the evidence in a murder case where a seam stress had been strangled in a bean field with her own scarf. George Popp successfully examined to examine the evidence in a murder case wherea seamstress had been strangled in a bean field with her own scarf. George Popp successfully examined soil and dust from clothes for identification to solve this real criminal case.”

· Paper envelopes should not be used because they easily tear and leak.

· If soil is adhering to items of clothing or shoes, a photographic and written account must be taken ofthe location of the soil traces and the whole garment should be packaged.

· Garments should be air dried in the laboratory as soon as possible.

· If the soil is wet/moist or adhering in a wet/moist condition to objects (e.g., tyres, vehicles, garments, or shovels)the soil should first be air dried and then packaged.

· However, in the case of obvious sequential layer or mixed fragments/particles of soil being present, the “surface layer” or mixed fragments/particles should be removed and then air-dried.

· Dry samples should be stored at room temperature ensuring that Containers are sealed.

· Appropriate caution should be taken when storing and transporting samples.

· If biological material is attached, the samples should be packaged using clean cardboard boxes/paper bags because such samples are prone to rapid deterioration.

Several standard methods are available for quick separation and concentration of soil materials or particles such as sieving, magnetic extraction, and heavy mineral separation.

Soil is nearly invisible:

Although a suspect may be unaware that soil material – especially the fine fractions (e.g.,<50μm) – has been transferred directly to the person (e.g., shoes or clothing) or surroundings (e.g., carpet in a suspect’s car), soil materials are easily located and collected when inspecting crime scenes or examining items of physical evidence.

Traces of soil particles can easily and quickly be located directly using hand lenses or light microslists¹².

Computerized soil database capacity:

Computerized maps and databases of soil materials, such as soil and geological maps and related profile data, can be readily accessed by police or earth scientists through the web, for example, Australian Soil Resources Information System (ASRIS).

One common reason why soil horizons are different atdepth is that there is mixing of organic material, inthe upper horizons, and weathering and leaching, in the lower horizons¹³.

COLLECTION OF SOIL SAMPLES:

A general rule for the collection of soil samples is that the surface conditions simulated in the control sample are similar to those in the crime samples.

The collection of samples is to be done from the surface only, keeping in view that is should be as near as possible to the actual spot. Large differences will make the results much less reliable.

The number of control samples may be large and from all suspected places such as places narrated by the victim or eyewitness.

Samples must be collected from the surface, as it is the surface soil, which gets stuck to the shoes or clothes. The depth to which one can go should not exceed approximately one\two inches of the top surface.

Collection of the control soil samples:

The collection of the control samples play a vital role in the process of further investigation of a crime. The nature of crime and the possibility of contamination vary from place to place.

The soil mud around a new well should be different largely from the soil of the surrounding field. The soil from the sole of a pair of shoes having passed through the surrounding of the new well or having gone to the field nearby would be clearly distinguished when compared by the forensic physicist. The scientific test in such cases can further reveal whether the accused using shoes has gone first to the field site or the well site¹⁴.

EVIDENTIAL VALUES:

The role of soil comparison is essentially to help in completing the links in the chain of events constituting a crime.

Initial Characterization for Screening of Samples:

Initial screening (i.e., morphological comparison examination) of whole soil samples is to visually compare samples (i.e., hand-held samples/specimens, soil profiles, and samples/specimens under a stereobinocular light microscope)^{15-16 .}

Soil Morphology – Soil Profiling:

Morphological soil descriptors are arguably the most common and probably the simplest – and it is for this reason that all samples are characterized first using the fourkey morphological descriptors of color, consistency, texture, and structure.

The use of petrography is a major and often precise method of studying and screening soils for discrimination in forensics. Using a hand lens or low-power stereo-binocular microscope enables the forensic soil scientist to better detect mineral properties (e.g., particle shape and surface texture) and provide more accurate mineral identification^{17-20 .}

MATERIAL AND METHODS:

The following materials used were soil samples, glass bottles, plastic bottles, paper envelope, stereo microscope, compound microscope, ph meter, white sheet/ tray, test tubes, test tube holder, test tube stand, glass slides, coverslip, light source, filter paper, distilled water.

Various soil samples were taken on white sheet/ tray and carefully observed under stereomicroscope.

Visual appearance method:

Two samples of soil can be compared by their colour examination visually first. Both the samples were heated to a temperature of about 800-900degree Celsius and compared their colour again. It could be similar or different. Similarly observed in colours in both samples is an indication that they may be similar in nature . Further examination is necessary for confirmation of similarity of these samples.

Microscopic examination:

Soil samples were examined under a microscope to ascertain general appearance, vegetable matter – presence, foreign material like glass, grass, brick particles, presence of minerals, presence of dead insects or their eggs.

Particle size distribution:

Before carrying sieving test samples of soil were dried thoroughly and lumps broken with a rubber cork since particle vary enormously in size and proportion of different sizes present- the particle size distribution is highly characteristics.

Preliminary examination of soil:

Small amount of soil was taken in a test tube and preliminary examination of soil was done by

i. pH of soil

ii. Water holding capacity

iii. Moisture content

Preparation of soil solution:

Some riverside soil was transferred into a beaker containing water using spatula. All the soil samples were transferred in the same way. The soil solution was mixed well using a stirrer like glass rod. A folded filter paper was placed into a funnel and then placed it on a test tube. Filtered the garden soil solution through the filter paper and the filterate was collected in the test tubes. The soil solution was then ready for testing pH.

Using pH meter for measuring soil pH:

The protected cap was removed from the electrode. Electrode was rinsed using distilled water. The pH meter was calibrated using pH7 buffer solution. Then the meter was adjusted with known pH of buffer solution 4.0 and 9.2.Again it was rinsed with distilled water. To the soil water suspension in the beaker, the electrode was immersed and pH value was determined from the automatic display of the pH meter.

Moisture Content of Soil:

Soil samples, weighing balance and burner were required.

Took the crucible containing soil and weighed it using weighing balance. The initial value was recorded. Took the crucible containing soil over the Bunsen burner. The soil was kept for sometime till it dried. The crucible was again weighed and the weight of dry soil was recorded. Same procedure was done with all the samples. And initial and final values were recorded. The difference between initial and final value indicated the moisture content of the soil.

Water Holding Capacity of Soil:

Dry soil samples, graduated cylinder, measuring flask, beaker, distilled water, funnel, funnel stand, wire mesh were required.

A funnel was taken and then placed it on a funnel stand. A wire mesh was put in it. First soil sample was taken and the put it in the funnel. A graduated cylinder was placed below that funnel. 200ml of water was taken in the measuring flask and it was poured slowly over the soil in the funnel. As the soil got wet, the water tricked down into the cylinder. The above process was repeated with other samples.

Confirmatory Examination of Soil:

Soil samples were collected and placed on a white sheet/tray and observed it under Stereo microscope.

Microscopic observation:

Soil specimens to be examined were usually placed in a metal tray, white for dark specimens and black for light specimens, and examined by incident (reflected) light. The tray may also contain a comparison grid, and is often treated with a sticky substance to hold the particles in fixed positions while they are being examined and counted.

Table 1:

Serial No.	Sample	Colour	Soil texture	Particle size	pH
1.	S1	Yellow	Crystal	Small	7.7
2.	S2	Brown	Crystal	Medium	5.34
3.	S3	Yellow	Floury	Fine	6.23
4.	S4	Black	Floury	Fine	6.83
5.	S5	Black	Gritty to touch	Small	6.73
6.	S6	Yellow	Soft and floury	Small	6.17
7.	S7	Light Yellow	Gritty to touch	Medium	5.80
8.	S8	Red	Gritty to touch	Big	6.35
9.	S9	Dark Brown	Gritty to touch	Big	5.84
10.	S10	Yellow	Gritty and floury to touch	Medium to big	6.14
11.	S11	Yellowish Brown	Gritty to touch	Big	6.58
12.	S12	Red	Soft and floury	Small	6.41
13.	S13	Yellow	Floury	Small	6.81
14.	S14	Yellow	Crystal	Small	5.64
15.	S15	Yellow	Crystal	Small	6.73
16.	S16	Yellow	Gritty to touch	Big	5.88
17.	S17	Yellow	Floury	Fine	6.71
18.	S18	Yellow	Crystal	Fine	5.93
19.	S19	Red	Gritty to touch	Big	6.48
20.	S20	Yellow	Floury	Fine	7.02
21.	S21	Yellowish Brown	Crystal	Fine	6.43
22.	S22	Yellow	Gritty and floury to touch	Small	7.21
23.	S23	Brown	Floury	Fine	5.22
24.	S24	Reddish Brown	Powder like	Small	6.32
25	S25	Yellow	Shiny appearance	Small	7.23
26.	S26	Yellow	Crystal	Medium	6.97
27.	S27	Yellowish Brown	Gritty to touch	Medium to big	5.91
28.	S28	Red	Gritty and floury to touch	Big	6.45
29.	S29	Yellow	Floury	Fine to small	6.87
30.	S30	Yellowish Brown	Floury	Small	5.72

RESULTS AND DISCUSSION:

The soil samples were taken from various places of Ranchi and their different characteristic features like colour, texture, pH, particle size, etc was studied under Stereo microscope.

In the present study, it was found that soil samples kept in glass bottles gave proper description while observing under microscope.

The sample S1, S5, S6, S10, S13, S14, S15, S16, S17, S18, S22, S25, S26, and S29 are of yellow colour but they differ in texture and the pH of all of the samples also varies. The particle size of the samples is highly individualistic as observed in the study.

In sample S8, S12, S19, and S28, the colour observed was red. The texture of the samples vary from gritty, floury to gritty and floury.

The pH of all the samples vary slightly and the particle size observes was of different size as mentioned in the table.

In sample S4 and S5, the colour was black and the pH of the samples varies slightly.

In sample S2, S9, S11, S21, and S24, the texture observed was in various shades of brown but the pH and particle size varies.

Soil materials are routinely encountered as evidence by police, crime scene investigators, and forensic staff. Most soils can be differentiated by their gross appearance.

A side-by-side visual comparison of the color and texture of soil specimens is easy to perform and provides a sensitive property for distinguishing soils that originate from different locations.

From the gross appearance, the soil collected from different places showed variation in their color as compared with munsell color chart.

Fig 1. Weighing soil Fig 2. Filtered soil sample Fig 3. Soil solutions

Fig 4. pH measurement of soil Fig 5 Soil samples under Stereo microscope

Fig 6. Microscopic soil analysis Fig 7. Soil samples on white sheet

CONCLUSION:

Soils mean different things to different people. As soil particles can readily adhere to, and transfer from, items such as clothing, shoes, vehicles and tools, they have the potential to be used as trace evidence in forensic investigation.

This dissertation was aimed to compare the soil profile and their characteristic features in different area of Ranchi District.

The finding indicated discrimination in the soils collected in different points in the texture, color, particle size and pH.

The findings provided fruitful result to identify the origin of soil and can be applied in crime investigation. In fact, soil samples taken at the surface may have entirely different characteristics and appearances from soil dug in the soil profile. One common reason why soil horizons are different at depth is because there is mixing of organic material, in the upper horizons, and weathering and leaching, in the lower horizons.

ACKNOWLEDGEMENT:

I express my heart full indebtedness and owe a deep sense of gratitude to my Supervisor, Sunita Rani for her guidance, valuable suggestion, supervision, kind help, encouragement and technical help which proved extremely helpful in writing this paper, and made my experience productive and stimulating.

I am grateful to my parents for their support and advice throughout the research period. My sincere and heartfelt thanks to Farha Fatma and Aisha Fatma for their help in data collection at various stages of research.

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Received on 25.09.2023 Modified on 30.11.2023

Research J. Science and Tech. 2024; 16(1):11-18.

DOI: 10.52711/2349-2988.2024.00003