ISSUE 53 Expert Witness Journal - Journal - Page 23
Blood Pattern Analysis:
How BPA Can be Used in Criminal
Investigations
by Clare Jarman at Forensic Access
By identifying and understanding the patterns at a
scene, on clothing or a proposed weapon, a forensic
scientist can comment on the activities which may have
been undertaken. Patterns containing characteristic
identifying details can be formed by:
• Contact between a bloodstained and non-bloodstained surface
Introduction
For many years now forensic science has formed an
essential part of any case moving through the court
system which involves the interaction of humans with
each other or with the environment around them.
DNA profiling can prove immensely powerful in addressing questions about who biological material has
originated from. However, it is the success of this technique that has pushed the central focus for many cases
away from questions about the source of a particular
piece of evidence, to a more nuanced evaluation of the
actions of individuals during and after an alleged
crime.
• Blood dripping from a wound onto another surface
• Blood dripping into a pool of blood
• Impacts into wet blood
• Blood cast off a moving object
• Blood expelled from the airways
In any incident where someone sustains a bleeding
injury, blood can be distributed to individuals involved
and to the environment around them. This is where
Blood Pattern Analysis (BPA) can be employed to address questions central to the court’s understanding
of events.
• Blood shed from an arterial injury
The amount and distribution of blood transferred will
depend upon such factors as the nature and duration
of any contact, the proximity of the people/objects involved, the nature of the injuries sustained and the
amount of blood that was shed.
Pattern Recognition
BPA involves the identification of patterns of staining.
Pattern recognition skills are, by their nature, subjective – but these skills rest on sound scientific principles
and are bound by objective criteria which guide a
forensic scientist in their decision making.
EXPERT WITNESS JOURNAL
It is also the case that specific types of action, such as
kicking, punching or the use of a firearm can, on occasion, give highly characteristic distributions of blood
containing fine detail. This can add strength to a
forensic scientist’s interpretations.
21
F E B R UA RY 2 0 2 4