A Simplified Guide to BLoodstain Pattern Analysis

A Simplified Guide to Bloodstain Pattern Analysis

Example Cases

The Use of BPA

Gun spatter

Gun spatter will vary depending on the caliber of the gun, where the victim is shot, whether the bullet exits the body, distance between victim and the gun and location of the victim relative to walls, floors and objects. Typically, forward spatter is a fine mist and back spatter is larger and fewer drops.

eg. X (Re), 2010 CanLII 96277 (CA IRB)

Arterial Spray

The spurt of blood released when a major artery is severed. The blood is pushed out the vessel by the pumping of the heart and often forms an arching pattern consisting of large, individual stains, with a new pattern created for each time the heart pumps

eg. R. v. O'Connor, 1989 CanLII 4776 (SK CA)

BPA uses principles of biology (behavior of blood) physics (cohesion, velocity) and mathematics (geometry, distance and angle) to assist investigation in answering questions such as:

Where did the blood come from?

What caused the wounds?

From what direction was the victim wounded?

What movements where made after the bloodshed?

Types of Stains

Bloodstains are classified into three basic types: passive stains, transfer stains and projected or impact stains.

Passive stains include drops, flows, and pools and typically result from gravity acting on an injured body.

Transfer stains result from objects coming into contact with existing bloodstains and leaving wipes, swipes or pattern transfer behind such as bloody shoe print or a smear from a body being dragged.

Projected or impact stains result from blood projecting through the air and are usually seen as spatters, but may also include gushes, splashes and arterial spurts.

The characteristics of blood spatter depends on the speed at which the blood leaves the body and the type of force applied to the blood source.

Principles of Bloodstain Pattern

What is BPA?

Bloodstain pattern analysis (BPA) is the interpretation of bloodstains at a crime scene in order to recreate the actions that caused the bloodshed. Analysts examine the size, shape, distribution and location of the bloodstains to form opinions about what did or did not happen.

Blood contains both liquid (plasma and serum) and solids (red blood cells, white blood cells and proteins). Blood is in liquid state when inside and when it exits the body, but it doesn't remain a liquid for long. It will begin to clot within a few minutes, forming a dark, gel-like substance that grows more solid over time. The presence of blood clots in blood stains can indicate that the attack was prolonged , or that the victim was bleeding for some time after the injury occurred. Blood can leave the body in many different ways, depending on the type of injury. It can flow, gush, drip, spurt, spray or just ooze from the wound.

By: Arianna and Susan