Crime Library: Criminal Minds and Methods

Murder by the book: Murder by Deception

What's in the Blood

The key evidence was the blood spatter found on the clothing of all three people in the scenario, as well as on walls and ceiling of the home, and both sides had experts to interpret it. Blood pattern analysis is a complicated discipline and requires experience with many different situations to be able to perform an accurate reading.

John Glaister Senior
John Glaister Senior

Different types of bloodstains indicate how blood was projected from a body. It may drip out, spray from an artery, ooze out through a large wound, or be flung off a weapon raised to strike another blow. In the 1930s, Scottish pathologist John Glaister classified blood patterns into six distinct types:

  1. Drops on a horizontal surface
  2. Splashes, from blood flying through the air and hitting a surface at an angle
  3. Pools around the body, which can show if it's been dragged
  4. Spurts from a major artery or vein
  5. Smears left by movement of a bleeding person
  6. Trails, either in form of smears when a bleeding body is dragged, or in droplets when it is carried.

Any of these patterns or shapes can be traced to their point of origin by considering such factors as the surface on which it fell, the angle at which it hit, and the distance it traveled from the source. Thus, bloodstain patterns can assist investigators to interpret the positions of wounded bodies and the means by which a victim and suspect moved through a crime scene. A reconstruction of the scene helps the investigators determine if witnesses or suspects are telling the truth or lying.

The shape of the blood drop itself reveals significant information. The proportion of blood reveals the amount of energy needed to disburse droplets of those dimensions. The shape of a bloodstain illustrates the direction in which it was traveling and angle at which it struck the surface. Basic trigonometry enables investigators to develop a three-dimensional recreation of the area of blood's origin.

Arterial spurts, for example, when compared with the anatomical location of the injury, may provide information about the position when the injury was inflicted and any subsequent movement by the injured party. Castoff patterns, drops that are thrown off a swinging instrument in the arc of a swing, can illustrate the position of the assailant.

According to basic texts, the shape of a blood drop can reveal a lot about the conditions. The experts don't necessarily all agree, but a rule of thumb with a generally smooth and non-porous surface might be the following:

  • If blood falls a short distancearound twelve inchesat a 45-degree angle, the marks tend to be circular.
  • If blood drops fall several feet straight down, the edges may become crenellated, and the farther the distance from the source to the surface, the more pronounced the crenellation.
  • A height of six feet or more can produce small spurts that radiate out from the main drop.
  • If there are many drops less than an eighth of an inch across, it may be concluded that the blood spatter resulted from an impact.
  • If the source was in motion when the blood leaked or spurted, or if the drops flew through the air and hit an angled surface, the drops generally look like stretched-out exclamation marks.

Although there were only three photos of the Winger/Harrington scene, it was enough for the experts to see where the blood from the wounds of both victims had landed and what shape it had taken. Even so, they reached opposite conclusions.

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