Application of Forensic Biology in Crime Scene Investigations

Forensic biology is a broad field of study covering other disciplines, including anthropology, odontology, pathology, botany, toxicology, psychiatry, computer science, engineering, and chemical and biological sciences such as microbiology and molecular biology. Crime scene investigators (CSIs) apply the knowledge of forensic biology to analyze and preserve physical evidence. Physical evidence revolves around skeletons, bones, and a decomposing body in the case presented. Therefore, forensic biology would be significant in examining the physical evidence to identify the victims’ bodies in such a case. Forensic entomology insects would be substantial in exploring the decomposing body in estimating the time of death or cause of death.

In this case, molecular biology and DNA analysis would also be significant in examining the physical evidence to identify victims and DNA from sources other than the victim. DNA testing is done on biological samples containing DNA. Relevant biological samples from the described scene include bodily tissues like bone marrow from bones found in the location. Hairs and blood, if present, are also necessary biological samples. Furthermore, botanical expertise is significant in determining whether the subject was present in a particular area. Plant materials like pollen are sometimes collected as evidence as they may be attached to clothing. The suspect’s clothes or vehicles can be vacuumed to check for microscopic pollen grains. Finally, odontologists would also be essential in identifying the victims by determining their sex and age by studying the bones and skeletal remains.

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Processing the Crime Scene

Upon arrival, the first thing to do is define the area to be declared as the crime scene. A crime scene includes any part of the area that is reasonably anticipated to contain valuable evidence. It is wise to contain a larger region and later narrow it down to identify a smaller scene rather than secure a small area and attempt to expand it. The events of previous actions taken at the crime scene should then be recorded. CSIs should determine whether the activities of the persons reporting the crime have altered the scene in any way. Actions involving the movement of the victim’s body (and skeletons for this case) should be noted, and all information should be communicated to the superiors as soon as possible. After the crime scene has been defined and secured, its access should be limited only to the authorized personnel involved in the investigation. The crime scene should be surveyed once more while taking photographs, detailed notes, and sketches. Finally, thorough searches for physical evidence and other evidence should be conducted. Evidence consists of all kinds of objects; therefore, any item near the scene should be recorded, documented, photographed, collected, and their location noted.

Avoiding Contamination of Evidence at the Crime Scene

The surrounding area should be cordoned off, and a tent erected over the discovered human remains to protect them against contamination and loss of evidence. The most fragile evidence should be collected first. For instance, fingerprints are delicate and could be damaged or destroyed if the crime scene is altered. Therefore, evidence collection should be prioritized over the most sensitive pieces. Moreover, the following procedural steps should always be taken to avoid the risk of contamination.

Correct usage of appropriate protective clothing. The investigation team in contact with the scene should wear gloves, masks, hair nets, clean lab coats, or disposable investigation suits.
Wear double gloves and frequently change gloves. Gloves should be changed before and after being in contact with the exhibit.
Staff training. Creating awareness among all staff involved in the investigation (especially crime scene officers) increases their knowledge of how biological materials are transferred and how contamination arises, thereby reducing contamination risks.
Evaluating the necessity of the pre-examination police. Limiting the number of people examining the crime scene reduces the risk of contamination.
Establishing appropriate procedures for best handling, sampling, transport, and storage practices of biological evidence.
Evidence should be put into new bags. The bags should be handled with clean gloves following the proper storage and transportation procedures. They should be handled as little as possible and placed into secondary packing when transportation is needed (Fonneløp et al., 2016).

Dealing with First Responders and the Challenges They Pose

First responders are usually the first law enforcement officers to arrive at the crime scene. Logically, crime scenes provide valuable information; therefore, the first officers’ primary responsibility is to protect the crime scene. However, as the Locard Exchange Principle explains, change must occur when an individual comes into contact with a scene. Consequently, first responders risk altering the crime scene and contaminating or destroying evidence if certain precautions are not taken. To avoid such risks, they must observe the following precautions: first, wearing gloves and frequently changing them; second, cleaning all equipment before and after handling samples or using disposable instruments; third, avoid touching surfaces that may contain evidence; four, avoid talking, coughing, or sneezing over the evidence; avoid touching any part of their body while collecting and packaging evidence; air drying evidence before packing and use new paper bags for packaging evidence.

The following is additional information on how first officers should conduct themselves at the crime scene.

Secure and protect the crime scene from anyone not directly involved in the investigation.
Attempt to identify possible routes used by the suspect.
Note the original condition of the crime scene.
Record any changes, especially regarding their activities (or other investigation staff).
Protect evidence from adverse environmental conditions.
Conduct all their activities outside the secured scene (eating, smoking).
Record the location of the evidence before moving it.
Place trace evidence like glass into large envelopes.
Keep an open mind as to items that might be valuable as evidence.
Being aware that they are potential sources of contamination.
Evidence items should be photographed at 90° with and without L-scales.
Seek expert personnel’s assistance for complex or challenging evidence collection or documentation.
Take photographs (90°, close-ups) to describe all features of crime scenes (Fisher & Fisher, 2012).

Recovery and Collection Human Remains

Soon after the remains are discovered, they should be covered and protected against contamination. The body should be retrieved as carefully as possible to avoid damaging it and loss of evidence. The soil surrounding the body should be removed in sequential layers using wooden or plastic tools or hand-collected and sifted for evidence. Latex gloves and other relevant protective clothing are required when collecting this kind of evidence. Furthermore, badly decayed bodies are delicate and should be handled as gently and little as possible. Collected evidence should be labeled for proper identification and chain of custody. Samples with potential hazards should be clearly labeled before transportation to the lab. Health and safety should be a priority, and extreme care should be taken when handling samples from decaying bodies. Decomposing bodies contain fungi, bacteria, and other pathogenic microorganisms (Gunn, 2019).

Preservation and Transportation of Biological Evidence

Evidence is mainly preserved for future analysis. For best preservation, the evidence should be kept as stable as possible. Different samples are unique and require special preservation precautions. However, “cool, dry, and away from direct sunlight” are often good guidelines. Evidence containing DNA should be kept dry and at room temperature. Antimicrobial agents may be necessary in some cases, while air-drying would be a necessity in other cases. It is, thus, essential to seek advice from experts on specific samples (Ramey Burns, 2012). When moving a decaying body, the hands and feet should be enclosed in clear plastic bags to protect biological evidence attached to the palms, soles, or nails. Plastic bags protect the skin from damage: during later stages of decomposition, the skin tends to slough off, and it may be impossible to take prints if the epidermal layer is damaged. The other body (with clothes, if present) is then placed in a clean bag for transportation to the laboratory. For easier transportation of skeletonized remains, wrap them with a white sheet and place them on a wooden board. Access to the evidence should be limited to authorized personnel only involved in the investigation. Moreover, any analysis, handling, or transportation of evidence should always be noted.

Contamination Risks at the Laboratory

Like at the crime scene, contamination risks also exist at the lab. Evidence collected can be contaminated as a result of poor laboratory safety measures. Uncontrolled entry and exit from the lab implies that many people would contact the evidence, increasing the possibility of contamination. Personal activities in the lab, such as smoking, eating, or drinking coffee, also increase the risk of contamination. Additionally, poor practices like not wearing gloves, masks, and other appropriate clothing and working on unsterile surfaces increase the risk of contamination. The skin and hair may fall off from an analyst who is not wearing the proper protective clothing. Also, coughing over samples when not wearing could potentially contaminate the evidence.

Avoiding Contamination at the Laboratory

Standard laboratory practices should be observed to avoid contamination issues. Below are the basic guidelines for combating contamination.

Correct usage of appropriate protective clothing. The investigation team in contact with the scene should wear gloves, masks, hair nets, clean lab coats, or disposable investigation suits.
Wear double gloves and frequently change gloves. Gloves should be changed before and after being in contact with the exhibit.
Proper cleaning procedures. Different analyses follow different cleaning procedures. For example, in DNA testing, all the equipment and surfaces used for examinations should be cleaned with effective DNA-degrading detergents before and after analysis.
Environmental DNA monitoring can then be used to measure the efficiency of the cleaning procedures used. This protocol should be followed in all areas where the exhibit has been handled.
Establishing appropriate procedures for the best handling and storage practices of biological evidence.
Conducting all personal activities outside the lab or examination room.
Being aware of potential sources of contamination.

The DNA Profiling Process

DNA Extraction

Potential sources for DNA include blood and bodily tissues, from fingernail scraping to skin, organs, and bones. DNA extraction involves three main processes: lysis, separation from other cell components, and isolation. Lysis consists of breaking open the cell by disrupting the cell membrane. The cell membrane is disrupted using dithiothreitol (DTT), detergents like sodium dodecyl sulfate (SDS), or heating. Proteins are then denatured using digestive enzymes like proteinase K or deactivated through heat. DNA is then separated from the other cellular constituents by centrifugation. The portion without DNA settles at the bottom, and the layer with DNA at the top.

Polymerase Chain Reaction (PCR) (DNA Quantification)

PCR is a technology that duplicates the extracted DNA to make many copies. Materials required for PCR include a DNA template (the extracted DNA), forward and reverse primers, a buffer, magnesium ions, DNA polymerase (a catalyzing enzyme), and the four nucleotide bases (adenine, thymine, guanine, and cytosine). This reaction is performed in a thermocycler instrument, where the process is often done in 28 cycles. The main steps of PCR are denaturation, annealing, polymerization, and amplification.

Figure 1: PCR amplification process

Note: Essential Forensic Biology, 3rd ed. (p. 128) by Gunn, A. (2019). Wiley-Blackwell.

In denaturation, the sample is incubated at 94–97 °C to denature the DNA and separate the double helix into two separate strands. Next, temperatures are lowered to 50–60 °C so that the primers can anneal to the single-stranded DNA. The temperatures are then raised to 70–72 °C to initiate polymerization. At this stage, the DNA polymerase uses the four nucleotides as building blocks and reproduces a complimentary copy of the template DNA. Then, the original DNA sequence is amplified by repeating the procedure (denaturation, annealing, and polymerization) in successive cycles.

Gel Electrophoresis

Electrophoresis is a technique of separating particles based on their polarity. Small particles of the same charge move toward the oppositely charged electrode faster than larger particles when placed in a solution. The amplified DNA is mixed with a sieving gel to sort out the DNA fragments according to their length. Since DNA is negatively charged, it moves towards the positively charged electrode (cathode). The shorter fragments move faster and further than the longer ones; the resulting patterns can be visualized using modern fluorescent dyes as x-ray films. The x-ray films are developed to create a DNA profile, then compared to other profiles in the DNA database (Combined DNA Index System (CODIS)) or other samples for possible matches.

STR and SNP Testing

Short Tandem repeats (STRs) are the non-coding regions of the DNA molecule with repeated sequences. STR analysis identifies the number of four-base (tetranucleotide) or five-base (pentanucleotide) repeats at specific locations (loci) on the DNA strand. These repeats vary across individuals, and the number of repetitions at particular loci is compiled into a DNA profile. This profile is then compared to other profiles of known individuals, and conclusions regarding whether the individual is the source of DNA on evidence items can be drawn (Gefrides & Welch, 2010). Single-nucleotide polymorphisms (SNPs) are locations on the DNA with variations throughout the human genome. These variations are unique patterns similar in individuals who are genetically related. SNP analysis identifies the variation sequences on particular loci to develop an SNP profile, which is compared to other reference profiles.

Y-STR Analysis

Y-DNA is transferred paternally from father to son; therefore, relatives will have unique Y-STR profiles. Additionally, Y-STR loci are unique to males only. Therefore, Y-chromosome STR testing is helpful in forensics to analyze a mixture sample containing DNA from two people, for example, in sexual assault cases where there is a mixture of male and female DNA. It also helps to determine how many people have contributed to the sample.

Mitochondrial DNA (mtDNA) Sequencing

Mitochondria are cell organelles with their DNA. This DNA is circular, stable, and less susceptible to degradation. It is maternally transferred from mother to child, providing information about distant relatives. Further, its stability makes mtDNA more suitable in analysis involving skeletonized remains and old biological material. mtDNA analysis encompasses comparing DNA sequences between individuals. The difference between the sequences is noted as a haplotype (mtDNA profile). These mtDNA haplotypes from the evidence sample are compared with reference samples from known individuals to determine whether the individual contributed the mtDNA from the evidence item.

Significance of Serology in DNA Profiling

Serology is the scientific study of blood. It also involves identifying and analyzing other types of body fluids, such as semen and saliva. Presumptive and confirmatory tests are carried out to determine the areas containing valuable body fluids. In addition to forensic DNA analysis, identification of bodily fluids is significant in determining the nature of the crime committed. For example, DNA analysis could identify a stain from the suspect on the victim’s clothes, thereby linking the suspect to the crime. However, identifying the stain as semen would indicate that the victim was sexually assaulted (Kobilinsky, 2011).

Challenges in Data Interpretation

The major challenge in DNA analysis is the interpretation of results. The analytical part of the process must follow standard operating procedures for the accuracy and validity of results. However, interpretation of results requires technical expertise, which remains a challenge (Butler, 2015). It relies on professional expertise and judgment. Therefore, it is likely to make errors, especially in situations where samples contain a mixture of DNA from more than two persons. Unfortunately, even with improved technologies such as fourth-generation sequencing (FGS) technology, replication and reproducibility of results are still challenges.

Role of Facial Reconstruction

Facial reconstruction from skull structures can be done traditionally by applying modeling clay or by 3D computer-modeling techniques that are more sophisticated. There are two approaches for facial construction: the tissue depth method and the anatomical method. The former method utilizes statistical data banks of average tissue depth between the skull and the skin surface to recreate a model. The anatomical method requires anatomical knowledge to build up the tissue layers (layer-by-layer) starting from the bone surface. Accordingly, facial reconstruction plays an essential role in identifying victims in cases where they are unknown.

A Scenario Presenting Successful Conviction of the Perpetrator

CSIs collected various biological materials from the crime scene, the most valuable being hair (found near the distal hand phalanges from one of the skeletons) and bodily fluid from the decomposing body. Forensic serology was carried out, and the fluid was identified as semen. Next, DNA analysis on the two samples (hair and semen) was used to create DNA profiles. Both samples illustrated an identical profile, implying that the same person was involved in crime against the victims. Fortunately, the offender had previous records of assault; therefore, their DNA profile already exists in the CODIS database. A comparison between the DNA profile from evidence samples and the reference profile was run, revealing a positive match. It is logical that the perpetrator sexually assaulted the victims and later murdered them.

A Scenario Presenting Wrongful Conviction

Following the fall of one of the deer hunters into the hole with human remains, biological evidence at the crime scene was contaminated. Also, the first responder failed to record Carl and Joseph’s actions at the crime scene. The Locard Exchange Principle suggests that change occurs when one comes into contact with a scene; therefore, it is realistic to argue that activities at the crime scene change or alter the prospect of the investigation. Since the actions of the men at the crime scene were not recorded, focusing on the deer hunters became reasonable. Consequently, one of the deer hunters had come into contact with the skeletons, leaving his DNA at the crime scene. Following DNA analysis, he was inevitably linked to the crime and convicted when his DNA was identified.

Conclusion

Various disciplines of forensic biology, such as anthropology, odontology, pathology, botany, toxicology, and chemical and biological sciences, like molecular biology, play a vital role in crime scene investigations. DNA profiling and additional knowledge from these fields of study help in the identification process of a victim or suspect and in determining whether a suspect was present at the crime scene. DNA profiling is a sequential process involving sample collection, DNA extraction, PCR reactions, gel electrophoresis, and sequencing of molecular markers. Further, analytical work and data interpretation require high professional expertise to avoid errors that may lead to wrongful convictions.

References

Butler, J. (2015). The Future of Forensic DNA Analysis. Philosophical Transactions of the Royal Society B: Biological Sciences, 370(1674), 5. https://doi.org/10.1098/rstb.2014.0252 Fisher, B., & Fisher, D. (2012). Techniques of Crime Scene Investigation (8th ed.). CRC Press.

Fisher, B., & Fisher, D. (2012). Techniques of crime scene investigation (8th ed.). CRC Press.

Fonneløp, A., Johannessen, H., Egeland, T., & Gill, P. (2016). Contamination During Criminal Investigation: Detecting Police Contamination and Secondary DNA Transfer from Evidence Bags. Forensic Science International: Genetics, 23, 121-129. https://doi.org/10.1016/j.fsigen.2016.04.003

Gefrides, L., & Welch, K. (2010). Forensic Biology: Serology and DNA. The Forensic Laboratory Handbook Procedures and Practice, 15-50. https://doi.org/10.1007/978-1-60761-872-0_2

Gunn, A. (2019). Essential Forensic Biology (3rd ed.). WILEY-BLACKWELL.

Kobilinsky, L. (2011). Forensic Chemistry Handbook (1st ed.). Wiley.

Lyman, M. (2011). Criminal Investigation: The Art and the Science (6th ed.). Pearson, 2018.

Ramey Burns, K. (2012). Forensic Anthropology Training Manual (3rd ed.). Pearson.

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Question

Listed below are the details of a crime scene that occurred over some time. You are to investigate and evaluate the crime and be prepared to present your information in court in the form of a written document. You will have to use entomology, odontology, anthropology, pathology, and microbiology techniques to complete your investigation.

Application of Forensic Biology in Crime Scene Investigations

Carl and Joseph were in the woods of Georgia in early fall. They had set up a camp because they were both deer hunters. In the fall of years when the weather is cooler, deer are very prevalent. On this cool November morning, the men were walking through the woods in their quest for deer. On the second day of being in the woods, walking through what was really thick brush and uneven terrain, one of the men slipped and fell into what appeared to be a covering of a hole in the ground. As he began to try and pull himself out, he saw several skulls and bones lying around. He immediately screamed for his friend, who assisted him in getting out of the hole. Together, they looked in and saw skeletons and what appeared to be a decomposing body.
The two men called the local police. The police arrived, secured the area, and called for the forensic team to come and investigate. You are the forensic person who has been asked to identify the five skeletons in the grave and the body that was only partially decomposed.
Assignment Guidelines
• Address the following in 10–12 pages:
Why will this particular case require the use of forensic biology? Explain in detail.
When you arrive on the scene, what is your first course of action? Describe your process, and be specific.
 How will you avoid contamination at this stage of the investigation? Explain.
 How will you control the other first responders or law enforcement officers? What challenges do they pose to a forensic investigator? Explain.
o What will you do to identify the remains at this crime scene? Explain.
 What is the documentation process for collecting and preserving this type of evidence? Explain.
How will you transport your evidence to the lab safely? Explain.
Once you arrive back at the lab, what significant risks of contamination exist? Explain.
 How will you avoid this contamination? Explain.
o What is the process for DNA analysis on the decomposing body?
 What specific tests will you use? Explain.
 How will serology play a role in the selected testing processes? Explain.
 Using this decomposing body as an example, what is the process that you will follow to conduct this DNA test properly?
 What challenges or barriers exist when you begin to interpret the results of your DNA test? Explain in detail.
How large of a role will facial reconstruction play in this investigation? Explain.
Next, provide two scenarios of court case outcomes regarding this investigation.
 One scenario must result in the successful identification and conviction of the perpetrator. You will need to fill in the blanks with regard to physical evidence and other necessary details.
 The other scenario must result in a wrongful conviction. You will need to identify the elements that lead to this wrongful conviction.
• Be sure to reference all sources using APA style.

Application of Forensic Biology in Crime Scene Investigations