Research Questions regarding the behavior of blood outside the body

Addendum to: Behavior of Blood Outside the Body Research Needs Assessment Form

OSAC BPA Subcommittee March 1, 2021

Page 1 of 2

ADDENDUM

Research questions regarding the behavior of blood outside the body

OSAC Bloodstain Pattern Analysis Subcommittee

March 1, 2021

Introduction

This document serves as an addendum to the OSAC Research Needs Assessment Form entitled 

“Behavior of blood outside the body” established by the Bloodstain Pattern Analysis 

Subcommittee on January 29, 2016 and reviewed July 26, 2019. The BPA Subcommittee is of 

the opinion this addendum provides additional details not captured in said form.

What is the problem?

1) Blood is a complex mixture of components that exhibits natural variation and may 

be further affected by environmental conditions, such as temperature changes, and 

dilution in scenes where bloodstain pattern analysis is employed. The range of 

variation in blood properties and the resultant connection to the range of variation 

in observed patterns and stains is poorly understood.

2) There is unexploited potential for extracting more information than is currently 

available in BPA by studying the mechanisms of pattern and stain formation and 

developing predictive and interpretive models to connect observable characteristics 

to stain and pattern forming mechanisms.

Why do we care about these problems?

1) The wide variation in the range of appearance of patterns and stains can result in 

incorrect identification of the mechanism of formation.

2) Knowledge of the properties of liquid blood and the effects of these properties on 

the mechanisms of blood transfer, drop formation, travel of drops through the air, 

deposition on surfaces, and drying are fundamental to BPA. This fundamental 

knowledge is critical to understand the range of variation in bloodstain and pattern 

appearance and to the development of predictive or interpretive models.
Research Questions regarding the behavior of blood outside the body

Addendum to: Behavior of Blood Outside the Body Research Needs Assessment Form

OSAC BPA Subcommittee March 1, 2021

Page 2 of 2

What are the research questions?

1) How is the appearance of spatter stains and transfer stains affected by deposition on 

surfaces as a function of material characteristics and conditions, geometry, blood 

volume and velocity? What experiments can be performed and models developed 

that connect observable stain or pattern characteristics to these deposition 

conditions?

2) What are the observable and quantifiable characteristics of stains and patterns from 

the mechanisms of impact, cast-off, cessation, forward spatter, backspatter, 

expiration, projected blood, transfer stains, wipe patterns, swipe patterns, and drip 

patterns? Which initial conditions during drop formation affect the resulting 

observable and quantifiable characteristics of the corresponding pattern? What 

models of these mechanisms can be developed that predict the connections between 

initial conditions and observable characteristics based on the fluid dynamic behavior

of blood?

3) What are the effects of blood characteristics on the appearance, distribution, number 

and size of stains from the mechanisms listed in question 2? Blood characteristics 

to investigate include: temperature, species, age since removal from the body, 

hematocrit levels, lipid levels, presence of preservatives, defibrination, alcohol or 

other drugs (blood thinners), other clinical conditions, cell damage, evaporation, 

separation, and clotting.

4) How are blood drops affected by travel through the air? What experiments can be 

performed and models developed to understand and predict droplet break up and 

deceleration/acceleration during flight?