Introduction
Deoxyribonucleic acid (DNA) is a crucial human body component in every cell. An individual’s DNA is similar in hair, blood, and bones. It carries genetic instructions for organisms’ functioning, development, reproduction, and growth. DNA, also known as biological evidence, is a powerful investigative tool since no two individuals share it.
Biological evidence plays a crucial role in criminal cases to exonerate the convicted or convict the guilty (Nwawuba Stanley et al., 2020). However, for the evidence to be effective in exonerating criminals, it should be appropriately documented, collected, and preserved. This research aims to assess the documentation, collection, and preservation of DNA evidence to preserve evidence integrity.
Documentation
Crime Scene Documentation
Documentation is vital from scientific and forensic points of view. Nothing should ever be altered until its authentic circumstance and function are recorded. Several distinct ways of documentation are available. Generally, the usage of a coupled technique is crucial.
Every major piece of evidence should be documented, making documentation the first step in processing DNA evidence (Meakin et al., 2021). Documentation captures information related to the location of evidence, its condition, and its appearance, and is recorded in the custody form. This document is crucial in evidence processing since it can track evidence movement from the crime scene to the laboratory (Potter & Underkoffler, 2021).
The transfer of evidence from the crime scene to the laboratory should be adequately documented with details of personnel handling evidence, time, dates, and changes in the condition of the evidence. This information is essential since it provides context for understanding the spatial relations and timeline related to DNA evidence. Maintenance of a clear and unbroken chain of custody begins at the crime scene.
Investigators should document observations related to the presence of DNA sources. The investigator’s notes should describe the location, appearance, and significance of each sample collected. Photographs and sketches can be a form of documentation for DNA evidence since they capture the crime scene layout, location of DNA evidence, and other essential environmental factors (Lee, 2019; Manea et al., 2022; Norris, 2020).
Investigators must take photographs from different distances and angles to facilitate a comprehensive visual record and document as many details as possible. The more detailed the recording, the more likely it is to preserve the integrity of the evidence and prove that it was handled effectively (Lone & Mir, 2019). Language is essential when recording since the examiner should use concise and clear language. Signing the documentation is crucial since it verifies that the information is accurate.
Case Files and Laboratory Documentation
Case files and laboratory documentation are essential for DNA evidence processing since they support evidence analysis, interpretation, and presentation. Establishing standard operating procedures (SOPs) to maintain consistency and document effectively is essential. (According to Stoykova et al. (2022), each case has a unique identifier, date, title, and case number. This is essential for referencing and easy retrieval.
Greytak et al. (2019) suggest that recording relevant individual information, such as their names, contact information, and demographic details, is vital for DNA evidence processing. The DNA samples likely collected by the examiner and sent to the laboratory should be well-documented and labeled. The examiner should document the name, amount, location, date, and collection method. This is essential in maintaining the chain of custody and preventing contamination of evidence.
Laboratory procedures and protocols used during analysis should be well documented. Zneimer & Hongo (2021) suggest that this is essential for maintaining consistency, allowing for verification, and ensuring high-quality analysis. Any deviations from the standard protocols, unexpected observations, or problems encountered should be documented during analysis. This is essential for providing transparency and dealing with potential concerns arising during the interpretation of results (Fleischman et al., 2019). Any deviations noted in DNA evidence processing should also be documented to address potential challenges.
DNA Collection
Crime Scene Investigation
DNA collection is a crucial step in the investigative process since it impacts the reliability and quality of evidence obtained. DNA collection necessitates using best practices and protocols to minimize contamination, preserve value, and maximize sample recovery. Crime scene investigators should know vital issues in identifying, collecting, transporting, and storing DNA.
When examining a crime scene, an investigator searches for potential sources of DNA evidence (Nwawuba Stanley et al., 2020). This can be conducted by identifying and documenting areas where DNA can be obtained, such as blood, hair, and saliva (Breslin et al., 2019). Crime scene investigation follows a systematic approach to increasing the possibility of collecting relevant samples.
This involves using appropriate protective equipment (PPE) such as gloves, shoe covers, and masks. According to Barbaro (2022), PPEs are crucial for crime scene investigation since they prevent the transfer of DNA materials from the crime scene to the investigator. Bare hands should not catch evidence since they can transfer it to the investigator’s skin, making it difficult to analyze effectively. The collection might not occur if DNA evidence has not been identified.
Collection Techniques
Once a potential source for DNA has been identified, the next step would be to collect it. DNA exists in various forms, such as saliva, hair, and blood (Breslin et al., 2019). Each site selected by the investigator for collection requires specific techniques to prevent contamination and maximize the recovery of DNA. Blood evidence is obtained from blood stains that should be carefully collected using sterile absorbent material or cotton swabs (Barbaro, 2022). Swabbing should be done carefully to allow for a complete blood collection. If the stains are large, multiple swabs might be used, and each swab should be air-dried and packaged.
Np et al. (2019) suggest that an individual’s saliva can be found on items such as drink containers and cigarette butts. To ensure accuracy in testing for possible saliva traces in a given location, one must use sterile cotton or nylon swabs. Swabbing and scraping techniques are typically used when collecting semen samples (Seiberle et al., 2022). Swabs provide an effective means to collect visible semen strains. Still, the investigator may use sterilized instruments such as scalpels for clothes and certain surfaces that cannot easily be wiped clean.
If hair is encountered as potential DNA proof, it should be cautiously gathered using clean forceps or gloved fingers to prevent contamination. As suggested by Admire et al. (2023), the hair follicle area is particularly precious for DNA evaluation. Collected hair must be placed in paper envelopes or breathable packing containers to permit drying (Barbaro, 2022).
Touch DNA refers to DNA left behind skin cells through pores and skin cells via contact with surfaces. Adhesive lifters can gather touch DNA samples (Rupert, 2023). Adhesive lifters are beneficial for amassing DNA from huge surfaces, which include weapons or doorknobs. DNA sample collection can be achieved through the use of photographs.
Evidence should be obtained from the least contaminated region to the most contaminated zone since DNA can be easily transferred from one surface to another. Collecting evidence from the most contaminated area to the least reduces the likelihood of contaminating the other regions. The investigator should collect evidence using a clean and sharp instrument.
Rao et al. (2020) suggest this prevents evidence destruction. The use of blunt instruments can crush DNA-containing cells, thereby making it hard to extract them. Parsons et al. (2019) suggest that a large evidence sample should be obtained during collection. When obtaining the samples, the investigator should not disturb the crime scene. Any slight disturbance at the crime scene might lead to contamination of evidence.
Sample Packaging
Proper packaging is vital for preventing contamination, loss, or degradation of samples. The packaging material used should be suited for preserving DNA integrity and preventing DNA degradation (Liu et al., 2020). Each sample of biological material should be packed individually to prevent cross-contamination with different samples. This is essential for preserving the sample’s integrity for effective analysis.
Paper envelopes or breathable packing containers are typically used for DNA evidence packaging (Barbaro, 2022). Plastic packing containers should be avoided unless necessary because of potential moisture buildup. Each bundle should be categorized with unique identifiers, including case numbers, exhibit numbers, and dates. It is critical to include facts about the region and a description of the sample in the packaging to offer context and aid in subsequent analysis and interpretation.
Packaging for the sample should be sealed using tamper-evident seals to promote evidence integrity. This is essential for the chain of custody since tampering with evidence can be detected. When packaging, the investigator notes the names of individuals involved and the date to promote data reliability and transparency (D’Anna et al., 2023). Labeling and differentiating each sample is crucial for multiple samples originating from different locations to limit confusion. Control samples should be obtained during the collection phase since they account for potential contamination and create a baseline for comparison.
DNA Evidence Preservation
DNA evidence preservation refers to protecting DNA from degradation and contamination. Various factors are likely to contaminate DNA, such as contact with other people’s biological evidence, improper handling and storage, and exposure to harsh environments such as sunlight, humidity, and heat. DNA is present on most human surfaces; thus, it is essential to prevent cross-contamination. This can be done by donning PPE such as gloves and using clean equipment when handling DNA evidence (Barbaro, 2022).
DNA can be degraded when exposed to humidity, heat, and sunlight (Mayes et al., 2019). As a result, it is essential to store it in a cool, dry place. Preferably, the evidence should be stored in a dark container for protection from direct sunlight (Adham et al., 2023).
Biological evidence can be degraded through improper storage and handling. This includes failing to label specimen containers and using the wrong specimen cans. Poorly stored biological evidence increases the likelihood of it becoming unused in court since it might be challenging to identify the source (Dahlman, 2021). This can weaken the prosecution’s case and give the guilty individual an upper hand. Therefore, following protocols for storing and handling DNA evidence is essential to prevent degradation.
When storing and preserving DNA, it is essential to maintain controlled conditions to prevent degradation and maintain its stability. Storage facilitates the need for optimal conditions to prevent degradation factors. DNA is affected by extreme heat; hence, it should be stored at low temperatures since such temperatures would slow down enzyme activity that would otherwise degrade it (Bruce et al., 2021). Humidity should be maintained at optimal levels to prevent moisture formation that could destroy the biological sample.
Refrigeration is the standard method for short-term storage of evidence samples. According to Kosecki et al. (2021), this method is effective because it slows microbial growth and enzyme activity. The other storage method is freezing, which is used for long-term purposes and limits enzyme activity since freezers operate at low temperatures.
According to Özdemir (2021), freezing is the commonly used method for sample preservation. However, it might be challenging to freeze samples instantly in field experiments due to the increased threat of thawing. As a result, freezers designed for storing biological samples should have a reliable cooling system to prevent thawing in case of power outages. Biological fluids such as plasma and serum can be stored through freezing.
Formalin fixation and paraffin embedding (FFPE) preservation techniques can be used to store clinical tissue samples. As Berrino et al. (2020) suggested, tissue fixation involves using formalin, resulting in cross-linkage between molecules, proteins, and nucleic acids. A neutral buffered formalin solution is preferred to an unbuffered one since it slows formalin degradation (Contreras et al., 2020). Degradation of formalin products impairs the quality of nucleic acids. Tissue specimens are placed in paraffin after fixation through dehydration, clearing, and embedding.
Drying can preserve specific types of DNA evidence, such as bloodstains. Anticoagulants, such as heparin, should be added to the samples to preserve blood stains. Drying involves using dry air to eliminate moisture from the DNA evidence container. Drying is essential since it inhibits enzymatic activity and microbial growth, thus reducing DNA degradation.
Proper DNA packaging is essential for preventing contamination. Another method of preserving biological evidence is ethylenediaminetetraacetic acid (EDTA). England et al. (2021) suggest that EDTA is a chelating agent that can bind ions such as magnesium and calcium to prevent DNA degradation. Human interference with biological evidence can be reduced by banning smoking near it, avoiding sneezing when handling it, limiting the use of staples for sealing evidence, and transporting it in a proper container.
Conclusion
DNA is a unique component of an individual’s body since everyone has their own genetic makeup. DNA evidence is crucial for convicting individuals suspected of being guilty of certain offenses. This necessitates adequate documentation, collection, and preservation of DNA samples. Evidence should be documented in the chain of custody every time an individual handles it.
Biological evidence can be collected by investigating and identifying the crime scene, extensively using collection techniques such as swabbing and packaging it to be sent to the laboratory or stored. Preservation techniques vary with the DNA evidence available and its intended storage duration. Each piece of evidence requires specific consideration to prevent degradation and contamination.
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