Tracing the Threads: Comparing Red Garments in Forensic Investigations

Abstract

The aim of this study was to compare the types, textile structures, labels, and fiber compositions of 64 red garments submitted as evidence in selected criminal cases between 2022 and 2024. The research enhanced the current knowledge of the characteristics of red clothing available to consumers and demonstrated the relevance of textile analysis in forensic science. Knitted fabrics were the most commonly used in the garments, followed by woven fabrics, nonwovens, and felts. Fiber identification focused on color and shade, generic classification, morphological structure, and chemical composition, revealing both similarities and distinctions among the samples. In a small percentage of cases, label information was found to be inaccurate. The study also examined the fiber content of threads, patches, logos, prints, and embroidery, underscoring the forensic potential of these often-overlooked elements. The identification of over 300 individual fibers enabled a critical evaluation of the analytical procedures and confirmed their effectiveness in forensic contexts.

1. Introduction

Clothing items, which are in close proximity to an individual during a criminal event, may play a direct role in the occurrence of the event itself. Consequently, they are among the most frequently encountered types of forensic evidence [1]. This can be accomplished through the examination of traces found on the clothing of those involved in the event, such as biological residues (e.g., blood, semen, saliva) or evidence of damage (e.g., cuts, tears). It is important to consider that biological residues may be transferred onto clothing through both primary and secondary transmission. The distribution patterns of such residues can differ significantly depending on the mode of transfer, which may affect the interpretation of forensic evidence. While these distinctions may not be evident at the crime scene, they often become apparent during a detailed forensic analysis. Consequently, the examination of evidence items frequently requires collaboration among specialists from various forensic disciplines, allowing for a comprehensive evaluation that integrates diverse expertise—whether it concerns biological residues, mechanical damage, or other relevant factors—to ensure accurate interpretation of complex trace evidence.

A particularly significant aspect of forensic textile analysis is the examination of fragments, especially those not visible to the naked eye, such as microtraces in the form of single fiber fragments [2]. During the course of the event, these traces may be transferred between contacting surfaces and can subsequently be found, for example, on the clothing or under the fingernails of the victim and the suspect, or on airbags that deploy inside the vehicle during an accident.

When interpreting the results of forensic examinations of textiles or the fibers that make them up, certain aspects related to consumer preferences in the field of clothing textiles should be taken into consideration. The most important of these are those that allow for the assessment of the prevalence of specific types of textiles and fibers, which in turn can help indirectly assess the likelihood of linking clothing to a particular individual. In recent years, consumers have become more conscious and selective in their spending. This shift has influenced their purchasing habits, including clothing choices. Growing diversity in consumer expectations, combined with the rapid spread of fashion-related information, further shapes these decisions [3]. Without a doubt, color is one of the most important characteristics considered when choosing clothing. However, color perception is highly subjective and can vary depending on individual sensitivity, lighting conditions, and the limitations of human vision. Differences in color perception between individuals are influenced by factors such as age, gender, vision impairments, and visual acuity [4,5].

Research on consumer preferences in the field of textiles is an important tool that allows for obtaining information regarding the direct interest of both current and potential customers in individual attributes of the clothing offered. Their limitation is the fact that this type of research is strictly tailored to the ordering organization [6]. Experts in the fashion market analyze collected data to identify factors that contribute to the greatest possible increase in customer satisfaction and loyalty. They also assess specific actions that may positively influence the further development of a given company. However, consumer research can only be used indirectly in forensic examinations of textiles and fibers, where the selection of research material is primarily based on the color of clothing and fibers. Only a selected subset of such research takes into account the color of the clothing purchased by consumers. For the second consecutive year, data from Allegro showed that Poles remain loyal to subdued colors [7]. Consumers most often chose black clothing, as well as items in shades of blue and gray. Among the 10 most popular colors indicated by customers, 8 were identical for both men and women, with the most notable differences in color preferences observed for white—preferred more by men, and red—appreciated more by women.

Color is also one of the most important parameters affecting the evidential value of fiber microtraces. According to international population surveys regarding prevalence, the two most common groups of colored fibers are black/gray and blue cotton [2,8,9,10,11,12]. The presence of red cotton fibers in a population of fiber traces distributed in the environment is also significant, as it indicates that they may be a common object of forensic interest [2,11,12]. Forensic identification of single fiber fragments, typically no more than a few millimeters in length, is possible using non-destructive methods such as optical microscopy and microspectroscopy [13].

The present study contributes to expanding knowledge about the characteristics of red-colored clothing owned by end consumers. The aim of the study was to assess the key features of such clothing, with particular emphasis on the fibers it contains. Therefore, the authors of this publication placed emphasis on the use of textile studies in forensic sciences. Based on the conducted research analysis and statistical evaluation, the authors aimed to draw general conclusions that could assist experts in the field of textile and fiber examinations in better understanding the complexity of such research materials. The obtained results may also help evaluate the effectiveness of research methods used to differentiate single red fibers, which is especially important in legal proceedings, where the identification and comparison of such fibers can play a crucial role in resolving criminal cases.

2. Materials and Methods

In this chapter, the original material used in the study is presented, along with a detailed account of the analytical methods applied for textile and fiber analysis. In Section 2.2, the origin and characteristics of the samples are outlined. In Section 2.3 and Section 2.4, the techniques of optical microscopy and Fourier transform infrared (FTIR) spectroscopy employed for fiber examination are described. Additionally, in Section 2.1, the statistical analysis methods applied in the study are presented.

The data used in this study are openly accessible and published under an open-access license, allowing for free use, distribution, and reproduction with proper citation.

2.1. Statistical Analysis

To assess the uncertainty of the proportions presented in the results section, standard errors (SE) were calculated for each clothing category using the following binomial formula:

$$SE=\sqrt{{\displaystyle \frac{p(1-p)}{n}}}$$

Subsequently, 95% confidence intervals (CI) were calculated as follows:

$$CI=p \pm 1.96\cdot SE$$

The lower bounds of the confidence intervals were truncated at zero to maintain logical consistency, as proportions represent probabilities and thus cannot assume negative values.

2.2. Original Material

The study utilized 64 garments, examined at the Institute of Forensic Research (Kraków, Poland), hereinafter referred to as IFR, over a period from 2022 to 2024. These garments were either fully red or featured red elements, such as patches, logos, prints, and embroidery. In total, 15 types of garments were examined. Both men’s and women’s clothing were assessed. The majority of the textile products consisted of scarves, shirts, headwear, and underwear (

Table 1. Types of examined clothing items and their respective quantities.

Number of Examined Items	Type of Examined Items	Sum of Examined Items	Proportion (p)	Standard Error (SE)	CI Lower	CI Upper
1	scarf	16	0.25	0.054	0.1439	0.3561
2	shirt	9	0.1406	0.043	0.0555	0.2258
3	hat	8	0.125	0.041	0.044	0.206
4	underwear	7	0.1094	0.039	0.0329	0.1858
5	sweater	6	0.09375	0.036	0.0223	0.1652
6	shawl	4	0.0625	0.03	0.0032	0.1218
7	collar	4	0.0625	0.03	0.0032	0.1218
8	undershirt	3	0.0469	0.026	0	0.0987
9	jacket	1	0.0156	0.015	0	0.046
10	jeans	1	0.0156	0.015	0	0.046
11	towel	1	0.0156	0.015	0	0.046
12	blanket	1	0.0156	0.015	0	0.046
13	bag	1	0.0156	0.015	0	0.046
14	dress	1	0.0156	0.015	0	0.046
15	apron	1	0.0156	0.015	0	0.046

). Since the research concerned a series of criminal cases, its scope covered all red elements of each garment, including threads used for sewing garment components, as well as elements in colors similar to red, such as reddish orange or pinkish red.

It should be noted that the examined garments are related primarily to criminal cases involving one suspect, which is reflected in the selection of items.

The forensic research conducted by the authors indicates that these investigations most commonly concerned clothing for which there was no information regarding the sources of fibers and the manufacturing processes used. In the present case, only 22 out of the 64 items of clothing examined bore labels indicating their fiber composition. The available information suggested that some of the examined garments may have originated from Italy, the Czech Republic, Germany, and Poland.

2.3. Optical Microscopy Methods Used for Textile and Fiber Analysis

The examination of the research garments began with the forensic photographing of each item using a Canon PowerShot G9 X camera (Canon, Tokyo, Japan) and their inspection in a room with artificial light (approximately 4000 lumens). During this inspection, representative samples of all textile products that were visually red or close to red were taken for further fiber identification and comparison. Microscopic samples of fibers were prepared using a low-power M125 C stereomicroscope (Leica, Wetzlar, Germany). Fiber samples were placed on microscope glass slides (Menzel-Glaser, Braunschweig, Germany) with a drop of pure glycerine (Merck KGaA, Darmstadt, Germany) as a mounting medium, and covered with coverslips (Menzel-Glaser, Braunschweig, Germany).

High-power microscopy examination of fibers present in the research material was conducted using bright-field and polarized light microscopy with an Eclipse E600 Pol (Nikon, Tokyo, Japan) and magnification of 100× to 400×. Images were recorded using a DS-Fi3 high-definition color microscope camera, and the NIS-Elements AR system was used to process the obtained data (both Nikon, Tokyo, Japan).

Fiber identification and comparison were carried out in accordance with the IFR’s own research procedure PB.KM.02, “Identification and Comparative Examinations of Single Fiber Fragments Using Optical Microscopy and Microspectrophotometry in the UV-VIS (Ultraviolet–Visible Spectroscopy) Range”, Issue 4 of 7 May 2021, accredited by the Polish Centre for Accreditation. The procedure is consistent with the European Network of Forensic Science Institutes—European Textiles and Hair Group (ENFSI-ETHG) guidelines in this regard [13].

2.4. FTIR Analysis of Fibers

The infrared spectroscopy analysis was performed after initial identification of fiber types using optical microscopy methods. All collected textile samples composed of man-made fibers were examined. Textiles that could be manually separated into individual threads composed of only one type of fiber were analyzed using a Nicolet iS50 FTIR spectrometer (Thermo Fisher Scientific, Waltham, MA, USA) with a built-in, all-reflective diamond ATR (Attenuated Total Reflectance). In the case of fabrics, weft and warp threads were tested separately.

For textile samples containing multiple types of fibers in the threads, a Nicolet iN10 Infrared Microscope (Thermo Fisher Scientific, Waltham, MA, USA) was used.

In both methods, the spectra were recorded by collecting 32 scans in the wavenumber range of 400 cm⁻¹ to 4000 cm⁻¹, with a spectral resolution of 4 cm⁻¹. For all examined samples, measurements were performed directly, in three repetitions from different areas. Prior to each measurement, a fresh background spectrum was collected to maintain accuracy. The polymer composition of the fibers was identified/confirmed using infrared spectral libraries in OMNIC Spectra Software (version 2012, Thermo Fisher Scientific, Waltham, MA, USA) or KnowItAll Infrared (IR) Spectral Libraries (version 2025.1, Wiley, Hoboken, NJ, USA). The acceptance criteria for the library matching in our database required a match factor of 900/1000 or higher.

3. Results and Discussion

The findings of the analysis, along with their interpretation, are presented in this chapter. The chapter is divided into six sections, each focusing on a specific aspect of textile identification: determination of clothing types (Section 3.1), identification of textile and fiber colors (Section 3.2), types of textiles present in garments (Section 3.3), the research process for fiber identification (Section 3.4), comparison of textile composition with label information (Section 3.5), and examination of sewing threads (Section 3.6).

3.1. Differences in the Determination of Clothing Types

Overall, the police officers securing the evidence in the criminal cases did a commendable job in assessing the type of garment. They made only eight minor errors in evaluating the examined clothing compared to the assessment made by the forensic experts. Ultimately, the police officers were able to accurately determine the type of examined clothing in 87% of cases. These differences involved items such as undershirts, underwear, sweaters, aprons, and scarves, which were later identified as T-shirts, trunks, polo neck jumpers, long-sleeve shirts, housecoats, and shawls. Differences in terminology may arise from regional dialects and, for instance, from the area where one grew up. Wardhaugh identified two types of dialects: regional dialects and social dialects [14]. A social dialect can be associated with ethnic groups and may vary depending on age. The regional dialect may differ in aspects such as word choice and syntax, among other things [15]. Therefore, it seems natural that some differences in terminology may arise among people living in different regions of a country, and even more so among people living in different countries. This is particularly true in the case of the complex and relatively intricate terminology related to garments and their construction. With regard to comparative forensic research on clothing, it seems important to standardize clothing terminology. Since complete standardization of terminology within a given geographical area seems unlikely, a forensic expert should strive to use simple language while also referencing the terms already applied by the police officer, the prosecutor, or the judge in a given criminal case.

3.2. Differences in the Determination of Textile and Fiber Colors

Significant discrepancies were noticed in the visual assessment of the color of clothing made by the police officers and the forensic experts (

Table 2. Differences in visual assessment of clothing color by police officers and forensic experts, including the number of discrepancies, proportions, standard errors, and 95% confidence intervals.

Color of Clothing Identified by the Police Officers	Color of Clothing Identified by the Forensic Experts	Sum of Mistakes	Proportion (p)	Standard Error (SE)	CI Lower	CI Upper
red	burgundy	4	0.1538	0.0693	0.0179	0.2897
red	pink	3	0.1154	0.062	0	0.2372
purple–red	multi-colored	2	0.0769	0.0527	0	0.1796
red	pinkish red	3	0.1154	0.062	0	0.2372
red	grayish pink	1	0.0385	0.0373	0	0.1117
red	beige	1	0.0385	0.0373	0	0.1117
red	reddish orange	1	0.0385	0.0373	0	0.1117
brown	reddish brown	1	0.0385	0.0373	0	0.1117
brown	multi-colored	1	0.0385	0.0373	0	0.1117
pink	multi-colored	1	0.0385	0.0373	0	0.1117
pink	reddish orange	1	0.0385	0.0373	0	0.1117
yellow–red	multi-colored	1	0.0385	0.0373	0	0.1117
green–red	multi-colored	1	0.0385	0.0373	0	0.1117
dark red	dark pink	1	0.0385	0.0373	0	0.1117
black–red	multi-colored	1	0.0385	0.0373	0	0.1117
white–red	multi-colored	1	0.0385	0.0373	0	0.1117
light burgundy	pink	1	0.0385	0.0373	0	0.1117
dark	black	1	0.0385	0.0373	0	0.1117

). These differences can be partly explained by the fact that the police officers were searching specifically for red-colored clothing, since a characteristic red fiber was found at the crime scene. Knowing that the comparative evidence involved this color, the police classified anything resembling this color as red.

This approach seems justifiable, as color perception is inherently subjective. Psychophysiological differences in color perception can lead to inconsistent results when determining the color of textiles. This subjectivity poses a challenge in forensic investigations, where accurate color identification can be crucial for linking evidence. Additionally, it should be noted that it is always safer to gather more evidence rather than less, and then narrow it down. This approach helps reduce the risk of overlooking key evidence in a criminal case. Moreover, in clothing dyed in colors such as brown, pink, or burgundy, the presence of red fibers cannot be ruled out, and this cannot be confirmed without the results of optical microscopy examinations, which are not usually conducted at crime scenes.

3.3. Types of Textiles Included in Clothing

An interesting issue that captured the authors’ attention was the proportion of different types of textiles used in the examined clothing (Figure 1). They indicate that knitted fabrics were the most prevalent type of textile in the sample (59%). Knitted fabrics are popular among consumers, largely due to their stretchability, warmth, versatility, and ease of maintenance, making them ideal for layering in colder climates. Fabrics with lighter or looser weaves can also provide cooling effects in the summer, particularly when their fibers possess temperature-regulating properties. It is therefore unsurprising that Germany, France, Italy, Spain, and the Netherlands are the largest importers of knitted fabrics within the EU. Furthermore, Poland has shown significant recent growth in this sector, positioning itself as one of the key markets in the region [16].

Nonwoven fabrics, which accounted for 9% of the textiles in the analyzed clothing, are increasingly important across various industries due to their superior properties and cost-effectiveness when compared to traditional textiles. They are also gradually making their way into the fashion industry [17].

3.4. The Research Path in the Identification of Fibers

The method of fiber identification involved the following examinations: macroscopic analysis, stereoscopic microscopy, bright-field microscopy, polarized microscopy, and infrared spectroscopy, as required. An example of the identification process is presented in Figure 2. In this case, the examined material was a scarf, for which the following components were identified: tassels, fabric, edge thread, and embroidery. The fibers composing these elements were determined to be viscose, polyester, and lyocell fibers.

The research identified a total of nine types of fibers in the examined clothing. Detailed information regarding the composition of the examined clothing is presented in Figure 3 and Figure 4. Cotton fibers were the most common, found in 25 of 64 garments. These fibers were primarily present in T-shirts, underwear, and hats. Wool fibers were identified in 20 garments, most frequently in sweaters, hats, collars, and scarves. Polyester fibers, found in 16 garments, were most commonly used in underwear, shirts, and collars. Polyamide fibers were present in 12 garments, primarily in hats, shirts, underwear, and scarves. Viscose fibers were identified in nine garments, primarily in scarves and hats. Acrylic fibers were found in eight garments, mostly sweaters. Other fibers, including regenerated cellulose, silk, and elastane, were less frequently encountered in the examined clothing.

3.5. Textile Composition Versus Label Information

Only about one-third of the examined clothing had labels indicating their fiber composition. The remaining items either displayed visible signs of the labels being cut off by the user or the labels were illegible due to prolonged use of the garments.

The discrepancies between the fiber type information provided on the labels and the actual composition of the garments, as determined by the authors through their identification research, reveal that 84% of the label information was accurate. Differences were observed, for example, in one case where some of the cotton fibers in a product labeled “100% Cotton” were replaced by polyester and polyamide fibers. In another case, wool fibers were partially replaced by viscose fibers. The labeling was entirely inaccurate in one instance, where acrylic fibers were fully replaced by cotton and polyester fibers.

The present research further confirms that relying solely on label information can often be misleading. Aside from extreme cases in which the label information does not correspond to reality, it is important to note that label information often omits fibers used in sewing threads or, for example, decorative elements such as logos. This omission is likely due to the fact that textile labels are mandatory in the European Union (EU) for textiles intended for sale to the end consumer, and EU Regulation 1007/2011 requires labels to indicate the fiber composition of textile products; however, the label must, in general, only specify the composition of the fabric itself [18].

Several studies conducted by The Circle Economy have examined the discrepancies between the garment composition stated on labels and the actual composition determined through analysis. Their findings indicate that, depending on the study, only 17% to 34% of labels contain fully accurate information [19]. It is worth noting that these studies involved over 10,000 garments. Additionally, 24% of garments were found to lack labels, which may be attributed to the removal of labels by the garment owners. Unlike the research presented in this publication, the studies conducted by The Circle Economy also considered the quantitative composition of textiles. One study indicated that 25% of labels overstated or understated the amounts of one of the components.

In summary, errors in garment labeling—such as those arising from mistakes during production, variability in labeling standards across countries, insufficient or improper testing of textile fibers, or changes in the supply chain and substitution of materials at various stages of production—can have far-reaching consequences. These range from consumer deception and health risks to legal and economic repercussions for businesses. These issues highlight the critical importance of accurate, standardized, and transparent labeling practices within the textile industry.

The identification of fiber types in clothing composition must always be a crucial step in forensic examinations. However, in most cases, a qualitative assessment is sufficient rather than a detailed quantitative analysis. The latter is of particular importance when determining which types of fibers present in the examined textile product are more likely to detach from the garment in larger quantities under the conditions of a specific criminal event.

3.6. The Examination of Sewing Threads

The study also includes an examination of the fibers that constitute the sewing threads of clothing, which, as previously mentioned, are often overlooked and omitted from clothing labels, yet they can provide significant forensic evidence. The examination of the threads in the evidence clothing focused exclusively on those that were red or in its shades. Various types of fibers were found in the sewing threads of the examined evidence clothing (Figure 5). The most common components were polyester and cotton fibers, with less frequent occurrences of fibers made from regenerated cellulose, silk, wool, and polyamide.

Keist pointed out that the sewing thread connecting two or more pieces of fabric in a garment may be composed of the same fiber content as the garment itself, but it is often different, as the thread must endure most of the stress and strain resulting from movement; therefore, it must primarily be strong and durable [20]. The authors’ research findings align with this assumption, as only in a few cases did the fibers in the threads and the garment match; this was observed, for example, in woolen threads in a woolen hat. The vast majority of garments exposed to stretching activities contained polyester or polyester-cotton blend threads, or exclusively cotton threads.

The observation that seamless technologies are widely used in the production of sports and intimate clothing [21] was also confirmed, as some items of the tested clothing did not contain sewing threads.

4. Comparative Studies of Acrylic Fibers

Special attention was given to the comparative studies of one fiber type, namely acrylic. The examinations focused on several fiber characteristics: color, morphology, diameter, the amount of delustrant, and chemical composition. Such studies are essential for forensic experts, as they assist in accurately identifying and comparing fibers from different sources.

Ultimately, a total of 10 examples of fibers identified as acrylics, in red or its shades, were found in eight items of clothing, out of approximately 300 fibers examined. Most of these fibers were characterized by a distinctive color and longitudinal shape, with fiber diameters ranging from approximately 18 µm to 35 µm. A comparison of two fibers, originating from different elements of the examined clothing, which exhibited the most similar morphological structures, is shown in Figure 6.

To summarize the results of the comparative examinations of the acrylic fibers identified in this study, it should be emphasized that the fibers varied in each analyzed clothing item.

Study Limitations

It should be noted that in forensic examinations, when confirming the consistency of morphological structure, diameter, the amount of delustrant, and color between comparative fibers, it is necessary to conduct additional checks beyond high-power microscopic analysis. In criminal cases, examinations using fluorescence microscopy and UV-VIS microspectrophotometry are always required, as well as chemical composition studies using microspectroscopic methods, primarily infrared spectroscopy, and, if necessary, Raman spectroscopy [13].

5. Conclusions

In this study, the examined garments were red in color, suggesting that textile dyeing processes had been applied to the materials. This factor was taken into account during the analysis, as dyeing can affect fiber properties and the interpretation of forensic results.

In this study, the authors evaluated the characteristic features of various clothing owned by end consumers, with a focus on its fiber composition. Using red-colored fibers as a case study, they provide a detailed analysis of the statistical data related to the composition of the examined garments. Overall, the publication highlights the application of textile studies in forensic science. Based on the research and statistical analysis conducted, the authors reached conclusions that may assist experts in the field of textile and fiber research in better understanding the complexity of such materials.

The differences in the naming of clothing types between the police officers and the forensic experts were minimal. It is noteworthy that variations in clothing terminology may arise from individual habits. The significant discrepancies in determining the color of evidential clothing likely stem from the police officers’ concerns about overlooking key evidence in the criminal case. An error regarding the color of clothing, which leads to securing additional evidence, increases the workload for the forensic expert. However, such an error carries fewer consequences than failing to secure clothing that may be crucial to solving the case. Therefore, it is advisable to secure and send to the laboratory a larger amount of evidence for analysis, even if it results in a longer processing period. Additionally, in clothing dyed in colors resembling red, the presence of red fibers cannot be excluded without laboratory results obtained through optical microscopy.

In identifying the fibers in the clothing, the authors also considered threads, patches, logos, prints, and embroidery, examining the constituent fibers in these elements as well. These are often overlooked due to their small size or quantity but should not be disregarded, as they can provide valuable additional information for solving forensic cases.

In the production of the examined clothing, knitted fabric was most commonly used, followed by woven fabric, nonwovens, and felts. The most commonly used fibers in the examined garments were cotton, wool, polyester, polyamide, viscose, regenerated cellulose, acrylic, and silk. It is important to note that, in most instances, multiple types of fibers may have been used in the production of a single garment. The threads used to sew the garments were most commonly composed of polyester, cotton, or a cotton-polyester blend.

Only approximately one-third of the examined clothing items had legible labels. Given the types of fibers identified in the textiles, the information provided on the labels was inaccurate to some extent, albeit in a relatively small percentage of cases. However, such labels should not be relied upon exclusively when examining clothing for forensic purposes, where a high degree of accuracy and reliability of results is required. In such instances, it is essential to conduct independent fiber identification analyses.

None of the acrylic fibers examined were identical, based on their characteristic features observed through optical microscopy and infrared spectroscopy techniques, which allowed for the evaluation of the effectiveness of the procedures and methods employed.