Identification and Interpretation of Fly Pattern Evidence at Crime Scenes

When violent crimes are committed, the crime scene is usually covered with blood.  Blood may be shed when the person is standing, sitting, or on the ground.  The weapon that caused blood to be released influences the shape of the bloodstains that form, as do many other factors.  Much more obscure are the ‘bloodstains’ dispersed about a crime scene that actually are not bloodstains at all; they are insect stains or artifacts.  Stains produced by insects, usually flies, are created by a multitude of mechanisms; at least ten that we know of.  When intermixed with real bloodstains, fly stains can be incredibly challenging if not impossible to recognize.  Why does that matter?  For one, patterns of blood can reveal directionality, especially important during reconstruction of the blood shed event.  The size and shape of bloodstains reveal details about how the stains were created.  Blood also contains DNA of either the victim or assailant.  Fly stains can provide false information about any of these parameters if confused as true bloodstains. It is even possible that insect artifacts introduce DNA to a crime scene from someone not associated with the crime.  Thus, it is absolutely essential to be able to distinguish insect stains from true bloodstains.  This conference is focused on pattern evidence created by flies at crime scenes.  We will examine how and when fly stains are formed on different materials, and within the context of the types of tissues and fluids associated with a corpse.  We will also discuss how to recognize the presence of insect artifacts and tools currently available for crime scene investigators to reliably identify insect stains under different contexts.  Ultimately, the information will help to recognize the presence of insect artifacts and avoid confusion with true bloodstains.

Learning Objectives:

1. Explain the difference between insect stains and fly artifacts.

2. Understand the challenges in detection and distinction of fly stains from true bloodstains.

3. Describe the methodology available for recognition of fly stains at crime scenes.