Introduction to Forensic Biology

• Forensic Science
• Biology
• Higher Education (non-degree)

Introduction to Forensic Biology

The use of biological principles and techniques in the context of forensic investigations.

Learning Objectives

By the end of this lesson you should be able to...

- Explain how biological sciences can be used in forensics

- Discuss how different disciplines of biology are forensically relevant

(serology, genetics, pathology, taphonomy, entomology, anthropology, botany, palynology, limnology, microbiology, zoology) 

Give an example of how you think biology could be useful in forensics...

Forensic Serology

The detection, identification, classification, and study of various bodily fluids such as blood, sweat, saliva, and urine, and their relationship to a crime scene.

The application of immunological and biochemical methods to identify the presence of a body fluid and potential further genetic characterization of the sample with a view to determining likely donors.

1. What is the nature of a biological evidence sample with regard to fluid or tissue origin?

2. What is the species origin of the sample, is it of human origin?

3. Who is the individual from whom the sample originated?

PRESUMPTIVE TESTS make use of a target chemical to establish the possibility that a specific body tissue or fluid is present.

CONFIRMATORY TESTS are then used to identify the specific biological material, which can then be typed.

Kastle-Meyer test showing a positive presumptive test for blood

Forensic Genetics

The production, comparison and evaluation of DNA profiles in order to identify biological material, as well as relationships between individuals.

Investigating the assumption that the biological material from a trace comes from a particular person, or whether a matching DNA profile can be found in a DNA database based on the statistical calculation of the rarity of the produced profile within a population.

1.  Whose DNA is it?

2. From what body fluid has it come?

3. How did it get there?

Assesses specific stretches of DNA  where there are repeating blocks of four bases known as short tandem repeats or STRs, the number of repeat units is variable due to mutations.

Forensic DNA analysis is concerned with measuring the length of DNA at these sites, which correlates with the number of repeats of the four-base blocks.

In order to determine the length of DNA at any one locus, a technique known as a polymerase chain reaction (PCR) is used to generate many copies of the relevant stretch of DNA from material recovered at the crime scene. 

These DNA fragments can be separated according to their size using a technique known as electrophoresis.

Forensic Pathology

 The branch of pathology that specialises in the medicolegal investigation of non-natural or suspicious deaths, and particularly the causation and consequences of wounds and injuries.

A forensic pathologist is a medical doctor who has completed training in anatomical pathology and has subsequently specialized in forensic pathology.

The focus of an autopsy is on :

• the cause of death
• the mechanism of death
• the manner of death 

The autopsy also provides an opportunity for  the collection of trace evidence or determining the deceased's  identity.

Examining and documenting wounds and injuries, along with the possible causation of those injuries.

Collecting and examining tissue specimens under the microscope (histology) to identify the presence or absence of natural disease and other microscopic findings.

Collecting and interpreting toxicological specimens of body tissues and fluids to determine the chemical cause of accidental overdoses or deliberate poisonings.

Forensic Taphonomy

The study of what happens to a body between death and recovery along with post-mortem decomposition processes which affect the preservation and recovery of remains and help reconstruct the circumstances surrounding the death.

Decomposition is studied in 'body farms', bodies go through a series of stages that are somewhat predictable, with temperature being the primary factor for the rate.

1) the condition, location, position and orientation of the body when deposited at the scene originally

2) what has happened to the body between the time of deposition and the time or recovery and how long it took (PMI), and importantly, whether humans were involved

3) whether we can provide information of events leading up to the body getting to the site.

Most of what happens to the body at an outdoor setting is the result of alteration or modification by natural agents such as plants, animals, soils, environment, gravity.

The recognition and documentation of the specific role played by each of these natural agents is critical to understanding and explaining why evidence ends up where it ends up, or why it looks as it looks at present.

Forensic Entomology

Utilises necrophagous insects that feed on dead tissue and decomposing remains to aid in forensic investigations. 

The study of insect species commonly associated with cadavers, their respective life cycles, their ecological distribution, as well as the changes in insect assemblage  (succession) with the progression of decomposition.

• Manner and circumstances of death.

• Post-mortem modifications of the body.

• Estimation of the PMI (time of death).

Forensic entomology is not limited to homicide applications. It has also been used in cases of neglect and abuse, in toxicology contexts to detect the presence of drugs, and in dry shelf food contamination incidents.

• Analysing the species composition of the necrophagous insects found on the body.

• Estimating the age of the juvenile insects developing on the dead body.
  

• Insect succession patterns are identified based on the time a given species of insect spends in a given developmental stage, and how many generations have been produced since the insects introduction to a given food source.

Forensic Anthropology

The application of physical anthropology techniques and to the identification of skeletonised human remains. The remains may represent victims of violence or natural / mass disasters.

Creating a biological profile for the deceased which includes sex, age at death and stature. Other assessments may include the analysis of trauma or pathologies

The stages of growth and development in bones and teeth provide information about whether the remains represent a child or adult.

The shape of pelvic bones provides the best evidence for the sex of the person. 

Abnormal changes in the shape, size and density of bones can indicate disease or trauma.

Bones marked by perimortem injuries, such as unhealed fractures, bullet holes, or cuts, can reveal cause of death. 

The bones are typically photographed and 

X-rayed. Some remains may undergo CT scanning or be examined with high-powered microscopes. 

These techniques provide detailed information about remains without altering them while providing a visual record.

Bullet entry and exit wounds in the skull of a homicide victim

FORENSIC 

MICROBIOLOGY

to clarify causes of death

(e.g. drownings, toxicology, infections)

to assist human identification 

(skin, hair and body fluid microbiomes)

for geolocation 

(soil or water microbiome)

to estimate post-mortem interval

(necrobiome)

Bio-terrorism occurs when biological components are used as warfare agents, microorganisms (e.g. Anthrax) that are deliberately dispersed to incapacitate or cause disease and death to humans, animals or plants.

Forensic Zoology

Wildlife Crime is anything that threatens the existence of a species, such as wildlife trafficking, poaching, wildlife cruelty, and habitat destruction.

The wildlife trade is third largest illegal trade behind drugs and firearms, and potentially makes $20 billion dollars per year. 

FORENSIC PALYNOLOGY

Pollen is designed to be dispersed (either via wind, insect, or another method) and is likely to adhere to a variety of surfaces resulting in easy and unnoticeable transportation.

A sample of pollen from a crime scene can help to identify a specific plant species that may have had contact with a victim or point to evidence that does not ecologically belong in that location.

Classification of species in a pollen assemblage obtained from an evidence.

Quantification by assessing their relative frequencies, allows for individualisation,

Scanning electron micrographs of pollen grains

locations of pollen accumulation in the human skull

Forensic Limnology

a
sub-field of freshwater ecology, examining the presence of diatoms in crime
scene samples and victims. 

Diatoms are diverse microscopic algae with silica cell walls and distinct morphology, with 8,000 known species.

Diatoms are identifiable based on each species' unique silica cell walls (known as "frustules").

The ratios of different diatom colonies present in samples are analysed.

  

To get an accurate result there must be at least 20 diatoms in a 100µL sample.

Freshwater diatoms as seen under the light microscope

Freshwater diatoms as seen under a scanning electron microscope

Pick one branch of biology from the list below...

1. Zoology
2. Microbiology
3. Palynology
4. Limnology

Research a real case study example of how this branch has been used in a forensic investigation.

Based on your research, describe

• the type biological evidence
• the biological discipline involved
• the biology techniques used
• the contribution to investigation