BPA/Forensic entomology essay

First sentence of introduction

Crime scene investigations use various forensic disciplines to reconstruct crimes and deliver reliable evidence to the courts for justice. Blood pattern analysis and forensic entomology are two key methods

What BPA and forensic entomology are used for

BPA examines bloodstain patterns to reconstruct violence, while forensic entomology studies insect activity on corpses to estimate time of death (post-mortem interval/PMI)

Their link

Their reconstructive role - BPA clarifies what happened and entomology clarifies when it happened

Structure of the essay

Compare and contrast their application, methods, reliability and significance to CSI

BPA

A specialised branch of forensic science concerned with interpreting bloodstains found at crime scenes to determine how they were produced

What type of crime BPA is applied to

Major, violent crimes like homicide or serious assault where the amount of blood present is sufficient to justify its investigation

Scientific premise behind BPA

Lies in the physics of fluid dynamics, which is particularly unique in blood

How is blood unique

Slightly thicker than water, behaves more like paint, viscous and elastic so its droplets hold together in flight, producing distinctive patterns on any surface it contacts

Blood’s properties allow…

Investigators to predict what patterns blood produces under different circumstances, e.g. high velocity spatter are fine, mist-like bloodstains usually caused by firearm shooting, while bloodstains creating “w” or “v” patterns are usually caused by arterial damage, where high pressure arterial spurting is driven by the heart

Classification of bloodstains

Passive (driven by gravity), active (moved by a force other than gravity), transfer (moved by the movement of assailants or third parties), e.g. transfer stain could be produced by an assailant fleeing the scene and could indicate their direction of travel

Case study for BPA

BPA used to convict Warren Horinek of murdering his wife in 1996 after police believed it was a suicide. The conviction rested on an analyst’s claim that small blood stains on Horinek’s shirt were high velocity gunshot spatter caused when he shot his wife

Forensic entomology

The study of insects, is grounded in biology, focuses on the developmental cycles, species and ecological succession of insects found on a corpse

Insects are like blood in that they are predictable

All respond to opportunities to gain food, shelter, a place to lay eggs, reproduce and develop through their life cycles

How forensic entomologists use insects’ predictability to their advantage

Some insects lay eggs in corpses, by knowing the life cycles of these insects and the decomposition stages at which certain insects populate corpses, forensic entomologists can estimate PMI

First insect to a corpse

Airborne insects like blow fly. They are attracted to rotting flesh as food course, their eggs hatch in 12-24 hours so finding eggs on a corpse indicates recent death (within last 12 hours)

How insects can determine when a crime occurred

Some insects only active at certain times of year (e.g. Mayfly in May), or only in the day/night, can help determine timeline of crime

Forensic entomology case study

Murder of Bobby Ryan by Patrick Quirke. Quirke argued that he opened his underground run-off tank and discovered the body, assuming whoever it was had fallen in, however entomologists found blowfly larvae in the body, indicating Quirke had opened the tank, allowing insects to get in, 2 weeks before he said he did

Contrasting their methodologies

• BPA experts classify bloodstains at a crime scene and calculate impact angles, forensic entomologists approach crime scenes differently, collecting insect species from corpses and analysing their developmental cycles in the lab to estimate PMIs

• BPA experts use methods like stringing to determine where victims were in crime scenes when impact occurred

Stringing

They calculate the impact angle at which blood struck the surface, attach a string to the edge of the bloodstains and extend it backwards at the calculated angle of impact and direction of travel

Similarities in their methodologies

Both converge in their use of environmental info

• Forensic entomology considers temp when estimating insect life cycles and decomp stages as both processes increase with higher temperatures

• BPA also considers temp as higher temps can accelerate the drying and clotting of blood, while lower temps can preserve bloodstains for longer

Main case study

Benecke and Barksdale (2003) on the double homicide of a mother and child in Germany in 2001

• Both bodies found in living room of their home, having been stabbed with extensive blood distribution

• Most of this was determined to be from passive and transfer stains, not high velocity spatter

• Lamp hanging between the bodies had tiny, reddish stains that could have been caused by the stabbing or insect activity

• Police requested BPA and forensic entomology expert statement

• Entomologist considered the activity of adult blowflies which feed on blood and regurgitate small droppings

• BPA expert analysed the shape and distribution of the stains

• Fly activity was deemed less likely to have produced the lamp’s stains compared to the stabbing

• Illustrates the complementary roles of BPA and forensic entomology in CSI and the importance of interdisciplinary collaboration

Weaknesses of BPA

• Methods such as stringing imprecise

• Assumes blood droplets travel in a straight line when in reality gravity causes them to travel in an arc (Jaromir, 2018) - this assumption can lead to overestimating the height of the origin

• Time-consuming

• Prone to human error

Weaknesses of forensic entomology

• Maggot feeding masses can increase core temp, accelerating decomp and reducing larval development time

• Incorrect collection, storage and lab processing of larvae can lead to incorrect estimate of insect life cycles and in turn, incorrect estimates of PMIs

• Indoor corpses and insects pausing their development (Bansode et al., 2025)

Conclusion

BPA and forensic entomology distinct yet complementary forensic disciplines that make significant contributions to CSIs through reconstructive nature. BPA provides insight into what happened at crime scene during violent events, whereas forensic entomology estimate PMI and when crime occurred. Together they allow investigators to address the “how” and “why” of criminal events