Effectiveness and Best Practices in the Methods of
Collection and Preservation of Hair Fiber Samples at the Crime Scene
Eficacia Y Mejores Prácticas En Los Métodos De
Recolección Y Preservación De Muestras De Fibras Capilares En La Escena Del
Crimen
Joselin Anabel Abarca Vistín
Licenciatura en Laboratorio
Clínico e histopatológico.
Maestrante Universidad
Nacional de Chimborazo
jaabarca.fslc@unach.edu.ec
https://orcid.org/0009-0006-6205-6976
Wilson Edwin Moncayo Molina
Doctorado en Química.
Magister en química aplicada.
Universidad Nacional de
Chimborazo
Wilson.moncayo@unach.edu.ec
https://orcid.org/0000-0003-2584-1861
This research was conducted
under the analysis of the effectiveness and best practices in the methods of
collection and preservation of hair fibers at the crime scene, with the aim of
optimizing the integrity of forensic evidence. To achieve this, a qualitative
study was carried out based on the analysis of scientific literature, forensic
manuals, applicable regulations, and technical reports to generate a
comparative approach to the methods used in forensic cases requiring the
collection of hair fibers as an integral part of the process. The intervention
emphasized the evaluation of different collection methods, with the most
commonly used being tweezers, adhesive tape, and forensic vacuums.
Additionally, preservation techniques were analyzed, including storage in paper
envelopes, test tubes, and the regulation of environmental conditions. The
results of the study revealed that the choice of collection method directly
depends on the type of surface and the amount of hair fiber present, while
proper storage is crucial to prevent chemical degradation or
cross-contamination that could affect the investigation. Therefore, it is
essential to standardize procedures alongside the training of forensic
personnel involved in this stage, as these factors are fundamental to ensuring
the reliability of the evidence, which would strengthen the chain of custody
and the validity of evidence in judicial processes.
Keywords: Fiber, data collection, legal procedure, collection, hair, crime scene.
Resumen
La presente investigación
se desarrolló bajo el análisis de la eficacia y mejores prácticas en los
métodos de recolección y preservación de fibras capilares en la escena del
crimen, con la finalidad de optimizar la integridad de la evidencia forense,
para cumplirlo, se llevó a cabo un estudio cualitativo basado en el análisis de
literatura científica, manuales forenses, normativa aplicable e informes
técnicos, para generar un enfoque comparativo de los métodos utilizados en
casos forenses que requerían la recolección de fibra capilar como parte
integrante del proceso. La intervención enfatizó en la evaluación de los
distintos métodos de recolección, siendo los más usados: las pinzas, cinta adhesiva y aspiradoras
forenses. Por otro lado, se analizaron las técnicas de preservación,
almacenamiento en sobres de papel, tubos de ensayo y la regulación de
condiciones ambientales. Los resultados del estudio permitieron evidenciar que
la elección del método de recolección va a depender de forma directa del tipo
de superficie y la cantidad de fibra capilar presente; mientras que el
almacenamiento adecuado es crucial para evitar la degradación química o
contaminación cruzada que afecta la investigación. Por ello, es fundamental la
estandarización de procedimientos acompañado de la capacitación del personal
forense que interviene en esta etapa, pues, son fundamentales para garantizar
la confiabilidad de las pruebas, lo que permitiría fortalecer la cadena de
custodia y la validez de la evidencia en los procesos judiciales.
Palabras clave:
Fibra, Recopilación De Datos, Procedimiento
Legal, Recolección, Capilar, Escena Del Crimen
Introduction
Forensic
science has evolved considerably in terms of how evidence is collected,
processed, analyzed, and used at a crime scene to further the investigation.
The most representative element of a crime scene has been hair fibers, as they
have the ability to show the connection between victims, suspects, and the
scene of the crime, as well as the ease with which they can be transferred
between surfaces and their high resistance in environments where criminal
events occur.
The
incorporation of hair fibers as an integral part of forensic evidence dates
back to the early 20th century, when advances in optical microscopy made it
possible to identify and compare fibers with greater precision. Initially,
techniques focused on visible physical characteristics, such as length, color,
and texture, which were evaluated with the naked eye or with the aid of a basic
microscope. This technique had the disadvantage of being limited in its ability
to differentiate between similar fibers, which reduced the usefulness of this
evidence in complex court cases.
With
technological advances and the development of new techniques that
revolutionized hair fiber analysis between the 1960s and 1970s, electron
microscopy and spectroscopic analysis became advanced tools that allowed the
chemical composition, optical properties, and internal structures of fibers to
be studied in unprecedented detail. This is why infrared spectroscopy and
chromatography made it possible to determine the presence of specific polymers
in synthetic fibers. In turn, fluorescence analysis made it possible to
identify chemical treatments applied to natural fibers. This development
significantly expanded the results in terms of the probative value of fibers,
allowing not only their origin to be identified, but also specific matches to
be established between fibers collected at crime scenes and control samples.
Despite
technological advances in the laboratory, the methods used to collect and
preserve fibers in the field have evolved at a much slower pace. For much of
the 20th century, investigators relied on rudimentary tools, such as tweezers,
paper envelopes, and plastic bags, to collect and store fibers found at crime
scenes. These practices, while functional, were highly dependent on the
experience of forensic personnel and did not always meet the specific needs of
each case. In addition, the lack of standardized protocols and reliance on
basic tools increased the risk of cross-contamination and loss of fibers during
transport and storage.
Incorrect
handling of hair fibers can seriously affect their integrity, i.e., their
physical and chemical appearance, prior to analysis in the laboratory. Several
factors, such as exposure to moisture, ultraviolet light, and friction that can
occur during transport, can cause damage and deterioration, reducing their
usefulness as evidence in a case.
In
this regard, synthetic fibers undergo photodegradation after being exposed to
ultraviolet light. On the other hand, natural fibers undergo changes in their
chemical structure as a result of oxidation in humid environments. As both
processes affect the physical and chemical properties of fibers, their analysis
and interpretation in forensic and conservation contexts would be affected.
The
lack of coordination between advances in laboratory analysis and limitations in
field techniques highlights the importance of innovation in fiber collection
and preservation. Although laboratory methods have reached a level of
sophistication that allows specific molecular characteristics to be identified,
the initial handling of fibers at the crime scene remains a weak link in the
chain of custody. This problem not only affects the quality of the evidence
collected, but can also compromise its admissibility in legal proceedings, as
courts require guarantees that the evidence has not been contaminated or
improperly handled.
The
uniqueness of hair fibers and their susceptibility to deterioration
The
analysis of hair fibers as forensic evidence is a crucial aspect of forensic
science, as it provides valuable information for investigations. Hair is a
common biological sample found at crime scenes, and its analysis can help
identify suspects or victims through morphological characteristics and DNA
matches; however, techniques related to its collection and preservation are
continually advancing to address the complexities associated with contemporary
crime scenes. Hair fibers can be of two types: synthetic or natural, and their
chemical composition, structure, and coloration can provide essential
information for linking suspects to the crime scene, victims, or weapons used.
Hair
fibers are mainly composed of keratin, a structural protein that provides
strength and flexibility. However, their chemical composition makes them
susceptible to external factors such as humidity, ultraviolet (UV) light, and
extreme temperatures, which can alter their physical and chemical structure.
These alterations include:
Physical
degradation: Prolonged exposure to ultraviolet radiation can compromise the
structural integrity of hair fibers and make them brittle. The mechanical
characteristics of hair, including tensile strength and elasticity, are
essential for preserving its overall durability. Methodologies such as optical
and electron microscopy are used to evaluate these characteristics and the
influence of external variables.
Chemical
degradation: Hair fibers can oxidize when exposed to high levels of
humidity and environmental pollutants, affecting their chemical composition,
causing changes in the physical properties of the hair, and complicating
subsequent analysis.
Contamination: Without
proper preservation techniques, fibers can become contaminated with external
particles or other evidence collected at the same scene.
Fiber
collection methods
Hair
fiber collection methods are classified into three main categories: tweezers,
adhesive tape, and forensic vacuum cleaners, which are described below:
Tweezers
Tweezers,
both traditional and advanced, offer precise handling of small objects, such as
fibers, with minimal risk of cross-contamination. However, their effectiveness
may be limited by the nature of the surface or material in which the fibers are
embedded and by the possibility of damage due to pressure. Although a
traditional method, tweezers are limited in their general applicability and
rely heavily on the skill of the technician.
Advantages
of advanced tweezers
Precise,
contactless manipulation: optical tweezers use light to manipulate particles,
offering precise, contactless control, which is ideal for delicate fibers and
minimizes the risk of contamination, an essential requirement for ensuring that
the research process and the results obtained are not altered.
Versatility
and adaptability: optofluidic tweezers combine optical and microfluidic
technologies, improving speed and efficiency in handling small particles that
may be found at crime scenes. Acoustic tweezers use sound waves for
non-invasive manipulation and are suitable for complex biological structures.
Environmental
responsiveness: microtweezers, made from smart
materials, adapt to environmental changes, allowing for controlled manipulation
without excessive pressure, which reduces the risk of damaging the fiber to
ensure manipulation-free sampling.
Disadvantages
and limitations
Ineffectiveness
on large surfaces: traditional tweezers can present problems when used on large
surfaces or for extraction in embedded areas, as can advanced tweezers, which,
despite technological developments, may have limitations based on their design.
Potential
to damage the fiber: While advanced tweezers reduce contact, the pressure
exerted by traditional tweezers can damage fragile fibers. Even with optical
tweezers, the intensity of the light must be carefully controlled to avoid
damage.
Adhesive
tape
Adhesive
tape is quick and efficient, but its effectiveness depends on the type of
surface and careful handling to avoid mistakes.
Advantages
Adhesive
tape allows fibers to be collected in large quantities and is effective on flat
surfaces, such as furniture, clothing, or smooth floors. Its ease of use and
portability make it a popular tool at crime scenes.
Disadvantages
The
main limitation of adhesive tape is the risk of cross-contamination. If not
used correctly, the fibers collected may mix with other samples or stick to
forensic personnel. In addition, some fibers may be damaged or lost when
removed from the tape.
Forensic
vacuum cleaners
Vacuum
cleaners are essential tools for collecting fibers and small particles from
large and difficult surfaces, such as carpets and car seats. They are equipped
with specialized filters that effectively separate and capture these particles,
ensuring a clean environment.
Advantages
Efficient
particle collection: vacuum cleaners are designed to efficiently collect coarse
and fine particles. The use of dual-chamber systems with pre-filters and fine
particle filters ensures that particles of different sizes are effectively
separated and collected. They use special filters to capture fibers and small
particles without mixing them.
Disadvantages
Laboratory
analysis requirements: once collection is complete, the useful fibers are
separated from the waste, which requires meticulous laboratory analysis, taking
considerable time and resources.
Size
and energy limitations: The size of vacuum cleaners and their dependence on
electrical power can limit their use in certain scenarios, such as in remote
areas or outdoors where power sources are not readily available.
Fiber
preservation methods
In
forensic settings, proper storage of fibers is as important as their initial
collection. Paper envelopes and test tubes are frequently used to store
evidence, each with different advantages and disadvantages. Paper envelopes are
preferred for their ability to minimize moisture retention, which reduces
microbial growth; however, they are prone to physical damage and do not provide
complete protection against exposure to high humidity or ultraviolet light.
Test tubes, on the other hand, offer excellent rigid protection for small and
fragile fibers, but require stable environmental conditions to prevent
deterioration.
Paper
envelopes
Humidity
control: Paper envelopes are an effective method of preventing moisture
accumulation, which is essential to prevent microbial growth in forensic
samples and thus ensure the integrity of the evidence.
Physical
vulnerability: despite their great advantages, envelopes are often prone to
physical damage if not handled with care, which compromises the integrity of
the evidence.
Environmental
limitations: paper does not provide adequate protection in conditions of high
humidity or rain and is vulnerable to exposure to ultraviolet light, which can
be problematic during transport or storage.
Test
tubes
Rigid
protection: test tubes provide solid protection against physical damage when
small and delicate fibers are present.
Environmental
sensitivity: To ensure the quality of the evidence, it must be stored under
stable temperature and light conditions to prevent degradation.
Influence
of the material: The type of material used in test tubes can affect the
persistence of cellular material, as has been observed in studies on tactile
DNA, in which metal substrates retain cells longer than plastic or ceramic.
The
choice between them often depends on the specific requirements of the evidence
being stored and the environmental conditions to which it will be exposed. In
addition, advances in materials science, such as the development of biocalcified foams, may offer new solutions for forensic
packaging in the future.
Environmental
conditions
Environmental
conditions are based on adequate control of temperature, light, and humidity
during storage. Therefore, hair fibers stored at room temperature, with
adequate protection from direct light, maintain their integrity for longer
periods of time. Environmental conditions have a direct impact on the
preservation of hair fibers, so the following factors must be taken into
consideration and properly controlled to maintain the integrity of the
samples:
Temperature:
Extreme temperatures, whether high or low, can significantly influence the
physical and chemical integrity of fibers. High temperatures accelerate
chemical degradation processes, while lower temperatures, although they slow
down these processes, can induce structural vulnerability. It is advisable to
store fibers at regulated temperatures, optimally between 18 and 22 °C.
Humidity: High
humidity levels pose a risk to hair fibers, as they promote the proliferation
of microorganisms and the degradation of chemical components. In addition,
excessively low humidity can cause the fibers to become brittle, so it is
essential to maintain a balanced humidity level where the hair fibers are
stored to prevent further damage.
Light: Prolonged
exposure to light, especially ultraviolet radiation, can cause discoloration
and compromise the integrity of the fiber composition. This not only affects
visual evaluations but also influences the results of sophisticated methods such
as infrared spectroscopy. It is advisable to store fibers in dark environments
or in opaque containers that block ultraviolet light to mitigate these hazards.
Impact
of cross-contamination
In
the field of forensic science, the collection of hair fibers is affected by
cross-contamination, which is a critical issue that compromises the integrity
of evidence. During the transfer of fibers for forensic examination,
contamination can occur due to factors such as the collection method, the
environmental conditions, and the hygiene practices of the examiner. Effective
strategies to minimize contamination are essential to ensure the reliability of
forensic analysis.
Factors
influencing cross-contamination
Collection
methods: The method used to collect hair fibers has a significant impact on
contamination levels. Bandaging and scraping are common techniques, as scraping
produces more loose fibers that can be transferred to the examiner's clothing,
increasing the risk of contamination outside the examined area.
Environmental
conditions: the movement of a hair fiber is conditioned by the distance it must
travel to its final destination, taking into account the influence of
environmental conditions. This is why cotton fibers are more likely to be
transported by air and remain suspended for longer than other fibers such as
wool or polyester, which can cause widespread contamination in a forensic
environment.
Decontamination
difficulties: Despite decontamination efforts, external contamination from
environmental sources or bodily fluids may persist, especially in autopsies.
Standard decontamination procedures may not completely remove contaminants,
complicating the interpretation of forensic results.
Strategies
to minimize contamination
Hygiene
and precautions: Implementing strict hygiene protocols and using appropriate
protective clothing can help reduce fiber transfer during forensic examinations
Controlled
environments: Conducting examinations in controlled environments with minimal
airflow and using specialized equipment can help limit fiber movement and
contamination
Advanced
analytical techniques: The use of techniques such as gas chromatography and
mass spectrometry (GC-MS) can improve the accuracy of hair analysis by
providing precise quantification and reducing the impact of potential
contaminants.
Standardization
and practice in Ecuador
Standardization
of procedures for the collection and preservation of hair fibers is crucial to
ensuring the integrity and reliability of forensic evidence. However, in
Ecuador, the implementation of these standardized practices faces several
challenges. These challenges are rooted in structural, technical, and training
factors within the country's judicial system and forensic environment.
Nevertheless,
challenges to adopting international standards for evidence management, such as
those described in the Manual of Forensic Investigation Procedures, may include
insufficient staff training, lack of resources for adequate equipment, and the
need for consistent compliance with protocols. These factors can hinder
effective implementation and compromise the integrity of evidence collection
and preservation.
Current
situation in Ecuador
The
adoption of international standards in forensic science in Ecuador,
particularly with regard to the chain of custody and evidence management, faces
several challenges. These challenges stem from the need for legal and
procedural reforms, the integration of advanced forensic techniques, and the
improvement of training and resources. The development of specialized units
such as DINASED and the Forensic Science Laboratory has been essential, but the
full implementation of international protocols remains a work in progress.
Challenges
in adopting international standards
The
implementation of modern protocols is contingent upon the adoption of
international standards. Therefore, the following problems arise in Ecuador:
Limited
equipment: in certain areas, specialized technological equipment, such as
forensic vacuum cleaners or advanced microscopes, is scarce, non-existent, or
malfunctioning, forcing investigators to rely on less effective manual methods
that could affect hair fiber collection.
Inconsistent
training: although training programs have been implemented, they do not always
reach all technicians in the field, especially in rural areas or areas far from
major forensic centers.
Logistical
challenges: Collecting evidence in areas with extreme conditions makes it
difficult to preserve fibers in optimal conditions.
A
study highlights that criminalistics in Ecuador is still in the process of
consolidation and that there is an urgent need for resources to equip forensic
units with modern technology and strengthen staff training.
Legal
Analysis of the Use of Hair Fibers as Forensic Evidence
From
a legal perspective, the analysis of hair fibers as an integral part of the
process, when considered as forensic evidence, must be analyzed from the
guiding principles of due process, including the chain of custody and the
admissibility of evidence, from a criminal context. Although fibers are
considered small and insignificant in appearance, they contribute to decisive
evidence in certain proceedings, provided that their handling, custody, and
analysis comply with legal standards that guarantee reliability.
Legal
Importance of the Chain of Custody
The
chain of custody is an essential principle that guarantees the traceability and
integrity of physical evidence from the moment it is collected until it is
presented in court, regardless of the procedure. In cases involving hair
fibers, their fragile characteristics make them particularly susceptible to
contamination or loss, which could undermine their probative value in ensuring
the accuracy of the process. According to Ecuador's Comprehensive Organic
Criminal Code (COIP), evidence collected at a crime scene must be handled in
accordance with established protocols that safeguard its integrity and prevent
any alteration, thereby maintaining the accuracy of the facts.
In
this context, the handling of hair fibers requires:
·
Clear and standardized protocols for collection, storage, and transport.
·
Use of appropriate tools, such as paper envelopes and airtight tubes, to
minimize the risk of cross-contamination.
·
Rigorous recording of each stage of evidence handling, including details on
environmental conditions and methods used.
Failure
to comply with these requirements may result in the exclusion of evidence, in
accordance with the principles of inadmissibility established in criminal
procedural law.
Nature
and Scope of the Research Problem
Although
there have been technological advances in fiber analysis in Ecuador, the
effectiveness of collection and preservation techniques remains a fundamental
issue for the advancement of forensic methodologies, as there are inadequate or
improperly executed procedures that compromise the integrity of evidence, which
may also result in its inadmissibility in court proceedings. The wide variety
of surfaces on which fibers can be found (carpets, textiles, hard surfaces) and
the fluctuating environmental conditions at crime scenes exacerbate these
challenges. In addition, cross-contamination during collection or storage poses
a continuous risk to the authenticity of samples.
Therefore,
this study has focused on addressing existing shortcomings in the collection
and preservation of hair fibers, in order to illustrate that, although they are
tiny and seemingly insignificant, they can play a vital role in cases where
alternative forms of evidence are unavailable or inadequate; Thus, in crimes
where there are no fingerprints or biological evidence, fibers can serve as the
only link between the suspect and the crime scene.
Furthermore,
improving forensic practices in this area has substantial implications not only
for solving individual cases but also for strengthening public confidence in
the criminal justice system. Properly managed and preserved evidence ensures
that judicial determinations are based on sound scientific principles,
mitigating the risk of judicial inaccuracies.
Similarly,
this study has a preventive impact, as perpetrators, recognizing that Ecuador's
judicial system employs appropriate methodologies for the process of
recognition, collection, and analysis of physical evidence, such as this
particular case of hair fibers, are less likely to commit crimes. That is why
the existence of established protocols that address and are aligned with due
process, accompanied by cutting-edge technology, sends a clear message
regarding the capacity of institutions to identify and prosecute those
responsible for illegal acts, while also serving as a deterrent to the
commission of crimes.
Increased
public confidence in the judicial system and the social and cultural
ramifications of this investigation are intrinsically interconnected, as both
facets are underpinned by the professionalization and improvement of forensic
practices. By ensuring that judicial decisions are based on solid,
scientifically grounded evidence, the perception of impartiality and
effectiveness of judicial institutions is reinforced, which in turn fosters
greater credibility and collaboration on the part of citizens. At the same
time, by developing specific protocols tailored to local contexts, this
research promotes the training of forensic specialists, generates applied
scientific knowledge, and raises standards of practice in the criminal justice
field in Ecuador. This virtuous circle not only strengthens society's trust in
its institutions, but also contributes to the cultivation of a culture that
views science as a fundamental pillar of justice and social progress.
Methodology
The
research was conducted using a qualitative approach, which seeks to gain a
detailed understanding of the phenomena related to the collection and
preservation of hair fibers at crime scenes. This approach has made it possible
to explore, analyze, and compare methods used in forensic contexts, as well as
to propose best practices based on the evidence obtained. The methodology is
organized into three main stages: data collection, analysis of results, and
development of proposals.
The
data collection stage will focus on obtaining detailed information through an
exhaustive search of literature in high-impact academic databases such as
Scopus, PubMed, and ScienceDirect, among others, as well as forensic manuals
and technical reports related to the topic under development. The objective is
to identify the most commonly used methods for the collection and preservation
of hair fibers and the optimal conditions that guarantee the integrity of these
samples.
· The
qualitative analysis involved categorizing the information into the following
areas:
· Efficiency
of different hair fiber collection techniques on different surfaces.
· Impact
of environmental conditions on the integrity of the fibers. An analysis of temperature, light, and
humidity.
· Identification
of evidence-based best practices for preservation.
Based
on the findings of the analysis, a proposal will be developed to optimize
methods for collecting and preserving hair fibers.
Results
In
Ecuador, the procedure that forensic technicians use to collect hair samples
follows general criminal investigation guidelines to ensure efficient
collection and proper preservation of hair samples within the chain of custody.
The process has several stages:
Initial
assessment of the crime scene: as this is the first phase, it serves to plan
and execute the investigation process correctly. To do this, investigators
identify the area of interest and physical evidence. To accomplish this, they
must:
Secure
the affected area: this involves cordoning off the crime scene to prevent
contamination, alteration of evidence, interference by uninvolved persons, and
possible changes that could affect the investigation.
Preliminary
identification of evidence: this is the part of the process that allows
personnel to conduct a visual inspection to locate possible hair fibers on the
different surfaces involved in the scene.
Determination
of critical points: identification of certain priority areas for collection,
guided by the sequence of events and contact routes.
Selection
of collection tools and methods: this is the stage in which the appropriate
instruments and techniques are selected for the collection of hair fibers based
on the characteristics of the crime scene, as well as taking into consideration
the surface on which they are found. To do this, it must be taken into account
that there are several tools that are used depending on the type of surface and
the amount of fiber present at the scene, including:
Tweezers:
used to collect individual hair fibers that are visible on small surfaces or
that are in direct contact with other evidence, such as clothing, floors,
adhered hair, and so on.
Adhesive
tape: this tool is usually used when the evidence is found on flat, large,
clean surfaces where the hair fibers are not embedded, thus ensuring that the
evidence is collected cleanly for processing without altering the results.
Forensic
vacuum cleaners: This type of tool is used for collection on surfaces such as
carpets, car seats, and hard-to-reach places. These devices have filters
designed to prevent the mixing of particles and thus ensure that the evidence
remains in its natural form.
The
use of these tools has several advantages and limitations that are adapted to
each context:
Table 1: Comparative
table of tools used for evidence collection
|
Herramienta |
Ventajas |
Limitaciones |
|
Pinzas |
- Alta
precisión para recolectar fibras individuales. -
Control en la manipulación que minimiza el contacto directo. - Bajo
costo y fácil disponibilidad. |
-
Ineficientes para recolectar fibras en superficies grandes o complejas, como
alfombras. -
Riesgo de dañar fibras frágiles debido a presión excesiva. -
Requiere habilidad técnica del operador. |
|
Cinta adhesiva |
- Eficiente para recolectar fibras de superficies planas y amplias
como muebles o pisos lisos. - Fácil uso y transporte. - Recolección simultánea de múltiples fibras. |
- debido a un manejo inadecuado, existe un alto riesgo de
contaminación cruzada. - Algunas fibras pueden dañarse al ser retiradas de la cinta. - Menor precisión en la identificación de fibras. |
|
Aspiradoras
forenses |
- Ideal
para recolectar fibras de superficies grandes y áreas difíciles como
alfombras y asientos de automóviles. - Gran
capacidad para recolectar partículas pequeñas y fibras incrustadas. -
Equipadas con filtros especializados. |
-
Requieren análisis laborioso en laboratorio para separar fibras útiles de los
residuos. -
Tamaño y dependencia de energía eléctrica limitan su uso en ciertos
escenarios. - Costo
elevado. |
Collection
procedure: this is the process that requires proper, orderly, systematic, and
controlled execution for the collection of hair fibers at the crime scene.
Therefore, it is essential to analyze the scene in order to select the tool
that will be used, as this ensures the integrity of the samples by preventing
damage or contamination. The collection follows a protocol that minimizes the
loss of evidence in order to maintain proper custody.
Use
of personal protective equipment: The forensic investigator assigned to collect
hair fibers must wear protective equipment such as gloves, a mask, and
disposable clothing to prevent cross-contamination.
Systematic
collection: When analyzing the crime scene and the surface where the hair fiber
to be collected as evidence is located, it is essential to select the
appropriate tool that will not affect or damage the sample to be collected.
Location
record: Each sample collected must be labeled with precise information about
its location, time, and method of collection.
Packaging
and preservation of samples: Packaging is a fundamental part of the process, as
proper preservation ensures that the hair fibers are free from possible
contamination by external factors, thus guaranteeing the integrity of the
sample until it is analyzed in the laboratory. To do this, the following must
be included:
Storage
material: the most commonly used are:
Paper
envelopes: these are used to preserve individual fibers that have been
collected with tweezers or adhesive tape. Using a paper envelope allows for
proper ventilation to prevent the growth of microorganisms that could affect
the collected sample.
Test
tubes or airtight bags: used for fibers collected in humid environments, to
maintain temperature and humidity control.
Labeling:
information about the case, sample number, and specific location within the
scene must be included.
Temperature
and storage: During transport, collected samples must be kept under controlled
environmental conditions. Samples must therefore be transported and protected
in properly sealed containers to ensure that the environment, i.e.,
temperature, humidity, and exposure to light, is controlled to prevent
deterioration of the fibers. Once in the laboratory, the fibers are stored
under controlled conditions until analysis, with strict entry and exit records
to maintain the chain of custody.
Recording
documents: these are the supporting documents that record all actions taken
during the collection, transport, analysis, and storage of hair fibers. This
process may include photographs, diagrams, and reports describing the location,
method, and materials used for collection, as well as the respective
preservation methods.
Critical
Points for Hair Fiber Collection
Despite
having a defined procedure for collecting hair fibers at the crime scene as
evidence in the investigative process, there are several critical points that
forensic personnel must take into consideration, including:
Improper
handling
Incorrect
use of tools: tweezers are one of the most commonly used tools due to their
benefits. However, despite their precision, in certain scenarios, such as
fibers embedded in complex surfaces, they can fragment the fibers, affecting
subsequent analysis.
Improperly
applied adhesive tape: Although it is an excellent tool for collecting hair
fibers on flat surfaces, careless use can lead to the adhesion of contaminants
or damage to the fibers when removed, causing contamination of the evidence
collected and affecting the results of the investigative process.
Forensic
vacuum cleaners: These are the most effective tools for large surfaces;
however, incorrect use can mix collected fibers, making laboratory
classification difficult.
Adverse
environmental factors
High
humidity: This condition promotes and allows chemical oxidation and microbial
growth in fibers, especially those of natural origin such as cotton or wool,
contaminating the evidence.
Exposure
to UV light: Synthetic fibers are vulnerable to photodegradation, which could
alter their chemical structure, reducing their evidentiary value.
Extreme
temperatures: in cold environments, fibers can become brittle or suffer
accelerated chemical deterioration at high temperatures, significantly
affecting the laboratory analysis process.
Available
infrastructure
In
rural areas, where advanced tools may be lacking due to transportation or
external conditions, the use of manual methods supplemented by strict hygiene
practices is prioritized.
Continuing
education
National
forensic units should receive regular training on international best practices
adapted to local needs; however, continuing education is not a priority for the
competent authorities.
Proposed
improvement to the procedure for collecting and preserving hair fibers at crime
scenes
The
following is the procedure to be followed, based on the guidelines issued by
the competent authority in Ecuador, as well as international organizations. The
purpose is to ensure the integrity of the evidence so that it is admissible in
court proceedings. Therefore, the following steps are suggested:
Table 2: Proposed
improvement to the procedure for collecting samples as evidence
|
Paso |
Actividad principal |
Subactividades |
|
Preparación en el lugar de la escena del crimen |
Delimitación del área |
Asegurar la escena del crimen, para ello, se puede
utilizar cintas y barreras para evitar el paso a personal no autorizado. Realizar una inspección visual del lugar, con la
finalidad de identificar áreas prioritarias para la toma de muestras. |
|
Equipamiento necesario |
Pinzas de acero inoxidable esterilizadas. Cinta adhesiva forense de baja adherencia. Aspiradoras forenses con filtros HEPA. Sobres de papel, tubos de ensayo herméticos
y bolsas opacas. Kit de protección personal: guantes,
mascarillas, batas desechables. |
|
|
Registro inicial |
Documentar la escena del crimen apoyados en
fotografías y notas específicas. |
|
|
Recolección de
fibras |
Elección del método (herramienta a ser usada
dependiente el lugar de la escena del crimen) |
Pinzas son usadas para recolectar fibras
individuales visibles en superficies pequeñas o delicadas. Cinta adhesiva forense, usada con
preferencia para superficies planas o amplias. Para ello, se debe aplicar
suavemente y despegar en un solo movimiento. Aspiradoras forenses para usar en áreas
grandes o superficies difíciles, como alfombras y tapicerías. Para el efecto,
asegurar el uso de filtros dedicados para cada zona. |
|
Procedimiento de recolección |
Realizar cambio de guantes entre la recolección de
muestras de diferentes áreas para evitar contaminación cruzada. Trabajar de forma sistemática de las zonas menos
contaminadas hacia las más contaminadas. Etiquetar cada muestra inmediatamente después de su
recolección, indicando la ubicación exacta y el método empleado. |
|
|
Preservación de
muestras |
Selección del material de embalaje |
Usar sobres de papel para la recolección de
fibras capilares con pinzas o cinta adhesiva. Los tubos de ensayo herméticos deben ser
empleados para fibras en ambientes húmedos o zonas de alta humedad. Las bolsas opacas son recomendadas para
proteger las fibras de la luz ultravioleta durante el transporte. |
|
Criterios de etiquetado |
Realice el registro de: Número único de identificación de la muestra. Descripción breve del origen de la muestra. Fecha, hora y método de recolección. Nombre del investigador responsable. |
|
|
Transporte y
almacenamiento |
Transporte al laboratorio |
Colocar las muestras en contenedores
sellados para evitar la exposición a factores ambientales. Usar una caja rígida para garantizar la
estabilidad de la muestra durante el traslado. |
|
Condiciones de almacenamiento |
Mantener las muestras en un ambiente controlado con
temperatura entre 18-22 °C y humedad relativa alrededor del 50%. Almacenar las fibras en áreas oscuras o con
protección UV. |
|
|
Documentación y
reportes |
Documentación completa |
Incluir material fotográfico y diagramas del proceso que detallen la
ubicación exacta de cada muestra recolectada. Elaborar un registro de la cadena de
custodia, asegurando que cada paso esté debidamente firmado y fechado. |
|
Informe preliminar |
Preparar un resumen inicial con detalles de las
muestras recolectadas, herramientas empleadas y observaciones relevantes
sobre las condiciones de la escena. |
|
|
Capación continua |
Entrenamiento practico |
Realizar simulaciones periódicas de
escenarios delictivos para reforzar habilidades en el manejo de fibras. Implementar capacitaciones para la
actualización sobre avances tecnológicos y prácticas internacionales. |
|
Evaluaciones regulares |
Establecer evaluaciones anuales del personal para
garantizar el cumplimiento de los protocolos y la adopción de nuevos
procedimientos. |
|
|
Incorporación de
tecnología |
Herramientas avanzadas |
Adquirir aspiradoras con tecnología de
filtrado avanzado y microscopios portátiles para análisis preliminares en
campo. Introducir contenedores con control de
humedad para transporte seguro. |
|
Digitalización de procesos |
Utilizar sistemas digitales que permitan registrar
la cadena de custodia y facilitar la generación de informes. |
The proposed process for
collecting hair fibers aligns with the methods for collecting and preserving
hair fiber samples at crime scenes proposed in the 2024 research by Jindal, as
they include the use of standardized protocols to ensure consistency and minimize
contamination. Therefore, forensic investigators are required to use clean,
sterile tools, such as tweezers, to collect hair fibers and place them in
labeled, tamper-proof evidence bags. Proper documentation of the collection
process, including the date, time, and location, is essential. Samples should
be stored in a controlled environment to prevent degradation and ensure their
integrity for subsequent forensic analysis.
The research conducted by
presents guidelines for collecting hair samples, emphasizing the importance of
using appropriate techniques to avoid contamination. To this end, it is
essential that hair fibers be collected with clean gloves and then placed in septic
containers and properly labeled. Preservation involves storing the samples in a
cool, dry environment, away from direct sunlight. Proper documentation of the
collection process, including the location and context of the samples, is
crucial to maintaining the integrity of the evidence for forensic analysis.
In 2023, the authors focus
their research on identifying the fundamental skills of crime scene
investigators and emphasize the importance of effective crime scene processing
for optimal investigative results.
For this reason, the
collection of hair fibers at the crime scene requires a combination of
necessary tools, accompanied by the application of the appropriate method for
preserving the sample. The adoption of these methodologies in Ecuador will
require a combination of investment in equipment, ongoing training for forensic
personnel, and the adaptation of international protocols to the specific
conditions of the country to ensure that forensic evidence meets
internationally required quality standards and can be used effectively in the
administration of justice.
Conclusions
The comparative analysis of
hair fiber collection methods at crime scenes depends directly on the type of
surface and the nature of the evidence presented at each crime scene. On the
one hand, tweezers are precise tools for handling individual fibers, but they
are ineffective on large surfaces or with embedded fibers. On the other hand,
adhesive tape allows for quick collection on flat surfaces, although it
presents a high risk of cross-contamination and possible loss of samples. In
addition, forensic vacuum cleaners are useful on large and complex surfaces,
but require meticulous analysis in the laboratory to separate useful fibers
from other debris.
Proper preservation of hair
fibers is crucial to ensuring the integrity of evidence in an investigation, as
environmental factors such as temperature, humidity, and light exposure that
influence fiber stability must be considered. For this reason, paper envelopes
are the most recommended method, as they allow ventilation and reduce moisture
accumulation, minimizing the risk of microbial proliferation. However, they are
vulnerable to high humidity and ultraviolet light. On the other hand, test
tubes offer greater mechanical protection but require storage in controlled
environments to prevent sample degradation.
Cross-contamination remains
a challenge in the collection and preservation of hair fibers, directly
affecting the reliability of forensic evidence. The main factors contributing
to contamination are the improper use of tools, incorrect handling of samples,
and adverse environmental conditions. To reduce this problem, it is recommended
to implement strict protocols, use personal protective equipment, and apply
systematic collection methods that minimize accidental fiber transfer.
Reference
Aljannahi, A.,
Alblooshi, R., Alremeithi, R., Karamitsos, I., Ahli, N., Askar, A.,
Albastaki, I., Ahli, M., & Modak, S. (2022). Forensic Analysis of
Textile Synthetic Fibers Using a FT-IR Spectroscopy Approach. Molecules,
27(13). https://doi.org/10.3390/molecules27134281
Balk, C.
(2015). Reducing Contamination in Forensic Science. Themis: Research
Journal of Justice Studies and Forensic Science, 3(1).
https://doi.org/10.31979/themis.2015.0312
Benthien, J.,
Sieburg, J., Engehausen, N., Koch, G., &
Lüdtke, J. (2022). Analysis of Adhesive Distribution over Particles
According to Their Size and Potential Savings from Particle Surface
Determination. In Fibers (Vol. 10, Issue 11). MDPI.
https://doi.org/10.3390/fib10110097
D’Orio, E.,
Calabrese, G., Lucanto, C., & Montagna, P.
(2023). Assessing performance in forensic hair examination: a review. International
Journal of Law in Changing World, 2(1), 102–119.
https://doi.org/10.54934/ijlcw.v2i1.38
Duran, A.
(2023). Cadena de custodia de los elementos de prueba. Una institución
jurídica en debate y desarrollo en el Ecuador. Revista Metropolitana de
Ciencias Aplicadas, 6(2), 277–285.
https://remca.umet.edu.ec/index.php/REMCA/article/view/659/652
Durán, A.,
Barrezueta, C., & Vivela, W. (2019). La
Naturaleza de la Criminalística y sus disciplinas. In Conference
Proceedings (Machala), 3(1).
Eche, R., Martinez, R., & Cedeño, M. (2023). Importancia de la
medicina legal y forense en la investigación de hechos violentos. RECIAMUC, 7(2), 544–556.
https://doi.org/10.26820/reciamuc/7.(2).abril.2023.544-556
Findik, F. (2024). Forensic materials and
test methods. Sustainable Engineering and Innovation, 6(1),
103–118. https://doi.org/10.37868/sei.v6i1.id265
Fiscalía
General del Estado. (2014). Manuales, Protocolos, Instructivos y Formatos
del Sistema Especializado Integral de Investigación Medicina Legal y
Ciencias Forenses.
https://www.cienciasforenses.gob.ec/wp-content/uploads/downloads/2017/10/registro-oficial-318-MANUALES-PROTOCOLOS.pdf
Gao, Z., Wang,
S., Sui, Y., Zhang, Q., Yang, Y., Huang, J., Xiong, Y., Ma, T., Zhang, X.,
& Zheng, H. (2023). A Multifunctional Acoustic Tweezer for Heterogenous Assembloids Patterning. Small Structures, 4(5).
https://doi.org/10.1002/sstr.202200288
Gonçalves, J.,
& Lopes, M. (2024). Physical and mechanical properties of the hair
shaft: A review of measurement techniques to verify the efficacy of cosmetic
products. Harmony of Knowledge: Exploring Interdisciplinary Synergie, 127.
https://doi.org/10.56238/sevened2023.006-127
Grigsby, W.,
Scott, S., Watson, H., & Middlewood, P. (2024). Printability,
Performance and Adaptive Moisture Response: Advanced Hygromorphic
materials using synergistic properties of keratin and lignin. Materials
Plus, 3(1). https://doi.org/10.37256/3120243698
Ha, G., Kim,
E., Kim, Y., Lee, J., Ahn, Y., & Kim, D. (2011). A study on the optimal
design of a cyclone system for vacuum cleaner with the consideration of
house dust. Journal of Mechanical Science and Technology, 25(3),
689–694. https://doi.org/10.1007/s12206-011-0122-8
He, Y., Cao,
Y., Nie, B., & Wang, J. (2023). Mechanisms of impairment in hair and
scalp induced by hair dyeing and perming and potential interventions. Frontiers
in Medicine, 10. https://doi.org/10.3389/fmed.2023.1139607
Jindal, Y.
(2024). Operational Procedures of Forensic Science Laboratories and
Protocols for Sample Collection. International Journal for
Multidisciplinary Research, 6(3).
https://typeset.io/pdf/operational-procedures-of-forensic-science-laboratories-and-4smja8xnvo.pdf
Kamalkant,
Sinha, J., Kumar, F., & Raj, J. (2024). Development and Performance
Evaluation of a Vacuum Drum Based Water Pumping System. Journal of
Scientific Research and Reports, 30(3), 68–75.
https://doi.org/10.9734/jsrr/2024/v30i31859
Kaufman, G., Jimenez, J., Bradshaw, A., Radecka,
A., Gallegos, M., Kaehr, B., & Golecki, H. (2023). A Stiff-Soft Composite Fabrication Strategy for
Fiber Optic Tethered Microtools. Advanced Materials Technologies, 8(12).
https://doi.org/10.1002/admt.202202034
Kelty, S., Ribaux, O., & Robertson, J. (2023). Identifying the
critical skillset of top crime scene examiners: Why this matters and why
agencies should develop top performers. WIREs Forensic Science, 5(5).
https://doi.org/10.1002/wfs2.1494
Kintz, P.,
Villain, M., & Cirimele, V. (2008). External post mortem artefact: a key
issue in hair result interpretation. Annales de Toxicologie
Analytique, 20(3), 121–125.
https://doi.org/10.1051/ata/2009014
Liberale, C. (2022). Micro-3D printed miniaturized
systems for optical trapping and manipulation. 33. https://doi.org/10.1117/12.2659395
Lukesova, H.,
& Holst, B. (2024). Identifying plant fibres
in cultural heritage with optical and electron microscopy: how to present
results and avoid pitfalls. In Heritage Science (Vol. 12, Issue 1).
Springer Science and Business Media Deutschland GmbH.
https://doi.org/10.1186/s40494-023-01122-z
Mahesh, S.,
& Ranjeet, S. (2015). Extraction, Analysis and Quantization of
Endogenous Level of GHB from Human Hair. Research Journal of Forensic
Sciences, 3(3), 1–6.
https://www.isca.in/FORENSIC_SCI/Archive/v3/i3/1.ISCA-RJFS-2014-009.pdf
Morison, R.
(2019). Improving the forensic value of textiles and fibres
through the holistic detection and analysis of acquired characteristics due
to environmental factors [University of Technology, Sydney].
https://typeset.io/pdf/improving-the-forensic-value-of-textiles-and-fibres-through-3i6cso3dmj.pdf
Mosse, A.,
Rennie, V., Poudoulec, Q., & Suárez Zamora, D.
(2024). Paper waste
grown as a biocalcified foam: perspectives from a
bacterial and design viewpoint. Research Directions: Biotechnology Design,
2. https://doi.org/10.1017/btd.2023.11
Muriel, M.,
Ordóñez, H., & León, J. (2018). Criminalística: disciplinas técnico científicas. Universidad
Libre de Cali.
Pilco, N.
(2014). Manual de tricología forense: Aspectos básicos para la
descripción de cabellos.
https://www.academia.edu/37005832/MANUAL_DE_TRICOLOGÍA_FORENSE_Aspectos_básicos_para_la_descripción_de_cabellos?auto=download
Plazas, R.,
Hernández, L., & Flórez, M. (2017). El debido proceso y la cadena de
custodia frente a las pruebas judiciales presentadas por el auditor forense.
IUSTA, 46. https://doi.org/10.15332/s1900-0448.2016.0045.02
Roux, C., Hutiunen, J., &
Rampling, K. (2001). Factors
affecting the potential for fibre contamination in
purpose-designed forensic search rooms. Science & Justice, 41(3),
135–144. https://opus.lib.uts.edu.au/bitstream/10453/6065/1/2004004413.pdf
Salem, A.
(2023). Maintaining the chain of custody: Anti-contamination measures for
trace DNA evidence. International Journal of Science and Research Archive,
8(2), 457–461. https://doi.org/10.30574/ijsra.2023.8.2.0257
Sharma, V., Mahara, M., & Sharma, A. (2024). On the textile fibre’s
analysis for forensics, utilizing FTIR spectroscopy and machine learning
methods. Forensic Chemistry, 39.
https://doi.org/10.1016/j.forc.2024.100576
Smigiel, D.,
Pospiech, J., Makowska, J., Stepnowski, P., Was, J., & Kumirska, J. (2019). The identification of polyester
fibers dyed with disperse dyes for forensic purposes. In Molecules
(Vol. 24, Issue 3). MDPI AG. https://doi.org/10.3390/molecules24030613
Uyama, M.
(2024). Recent Progress in Hair Science and Trichology. Journal of Oleo
Science, 73(6), 825–837. https://doi.org/10.5650/jos.ess23203
Vasiliev, D. E.
(2023). Biological risk factors and methods to ensure the infectious safety
of personnel in forensic and pathology departments. Pacific Medical
Journal, 2, 25–30.
https://doi.org/10.34215/1609-1175-2023-2-25-30
Zanders, A.,
& Klaviņa,
G. (2024). Legal and practical issues of special investigative
techniques—control of means of communication performance and usage of the
obtained information from criminal proceedings. SOCRATES. Rīgas
Stradiņa
Universitātes
Juridiskās
Fakultātes
Elektroniskais Juridisko
Zinātnisko
Rakstu Žurnāls / SOCRATES. Rīga
Stradiņš
University Faculty of Law Electronic Scientific Journal of Law, 1(28),
75–79. https://doi.org/10.25143/socr.28.2024.1.75-79
Zhao, J., Hou,
H., Huang, Q. Y., Zhong, X. G., & Zheng, P. S. (2022). Design of Optical
Tweezers Manipulation Control System Based on Novel Self-Organizing Fuzzy
Cerebellar Model Neural Network. Applied Sciences (Switzerland), 12(19).
https://doi.org/10.3390/app12199655
Zhu, Y., You,
M., Shi, Y., Huang, H., Wei, Z., He, T., Xiong, S., Wang, Z., & Cheng,
X. (2023). Optofluidic Tweezers: Efficient and Versatile
Micro/Nano-Manipulation Tools. In Micromachines (Vol. 14, Issue 7). Multidisciplinary Digital Publishing Institute (MDPI). https://doi.org/10.3390/mi14071326