First this to confirm the type of spatter found on Robin's shoe travelling in the wrong direction to have been from his own wound. The forensic evidence against Robin Bain is overwhelming.
Low Velocity - This type of spatter is usually caused by an impact to the blood source at a rate of 5 feet per second and is usually about 4 millimeters in diameter.
Medium Velocity - This type of spatter is usually caused by an impact to the blood source at a rate of 5-25 feet per second. Stains caused by this type of force are usually 1-3 millimeters in diameter, but may be larger or smaller.
High Velocity - This type of spatter is usually caused by an impact to the blood source in excess of 100 feet per second and is usually less than 1 millimeter in diameter, although it can be larger or smaller.
When blood hits a surface at an angle other than 90 degrees, the direction of it's path will be able to be viewed, interpreted and measured, which allows investigators to reconstruct what and how something occurred.
Although the picture to the left is is computer generated and not very realistic in appearance, it was made to look the way it is to exemplify how the direction of the path of blood can be indicated by "tail" of the stain. In this example, the blood traveled from the lower left to upper right. If an investigator was attempting to determine where the source of the blood was when the stain was made, an equation can be used, which will give an accurate location.
Now this to explain what spatter can reveal about a crime/suicide scene.
High-velocity spatters are usually caused by gunshot wounds, although they can be caused by other weapons if the assailant exerts an extreme amount of force. They travel more than 100 feet per second and usually look like a fine spray of tiny droplets, less than one millimeter in diameter. Bullet wounds are unique because they can have both back and front spatters, or just back spatters. This depends on whether the bullet stopped after entering the victim's body or traveled through it. In most cases, the back spatter is much smaller than the front spatter because the spatter travels in the direction of the bullet.
The Way of the Gun
If a gunshot occured at close range, the victim might have stippling, or burns on his skin from gunpowder. Shots fired at very close range can also cause internal muzzle staining. When this happens, the victim's blood is sucked back into the gun's muzzle by the cooling of the explosive gases that are released when a short is fired. Testing the gun's muzzle for blood can provide an additional clue to solve a case.
Analysts always look for voids, or empty places in the spatters that indicate that something (or someone) caught the spatter instead of the surrounding surfaces. In the case of a high-density spatter, this may mean that the assailant got some of the victim's blood on himself or herself. Sometimes, a blood spatter can look like it was high velocity when it was actually a medium- or low-velocity spatter. Cast-off droplets can fall from larger drops of blood. A savvy analyst looks for larger drops of blood among the many tiny drops to see if they are castoffs. These types of droplets are also found often on places like ceilings when the rest of the spatters are concentrated elsewhere.
Blood spatters can also overlap each other, which can show which gunshot or stab wound took place first.
Size and the force of impact are only two aspects of determining information about blood spatters. Next, we'll look at the shapes of spatters and how analysts use strings, trigonometric functions and computer programs to map out a blood-spattered crime scene.
I've abridged the above because it makes the necessary points about the size of spatter and how that is indicative of velocity. The spatter on Robin's shoes was high velocity by that description which was echoed by defence evidence. That evidence also attested to the direction of the spatter indicating that the spatter on Robin's shoe came from one of his victims because his wound was left temple while the spatter found on the shoe was going left to right, that's affirmative - left to right.
The second quote above repeats in some detail the first, or confirms the common knowledge of what spatter is. However, the second goes onto speak about shielding, ie areas shielded from blood spatter. We know there was no indicative shielded that allowed a gun man to be in the room with Robin, we also clearly know the hard contact necessary for the vacuum effect - there is more on that in the trial transcript with clearly defines the type of contact wound Robin had by not only the characteristics of the wound but also the vacuum effect of drawing spatter inside the rifle.
Interestingly, the second quote moves onto mention 'look at the shapes of spatters and how analysts use strings, trigonometric functions and computer programs to map out a blood-spattered crime scene.' This analysis opportunity was available to the Bain Police team, if not locally then certainly internationally, we all know now they didn't take that opportunity and that if they had David would have been exculpated as a suspect. This is the unnecessary haste that I've written about earlier, the Police should have exhausted the forensic evidence of the lounge at least, but they had already charged David before they had even the basic results. Unfortunately, they never turned back, no one resisted the haste of 'gut feelings' or 'suspicion' and looked quietly at the evidence to reconstruct Robin's obvious suicide, instead obvious things were given sinister meaning - the magazine on it's edge, the body close to the rifle, all guess work and no science, then all effort to cover the guess work with language such as 'paper run alibi' even to the point that the innocence of David Bain admitting the rifle was his and that no one else had access to it became 'proof' and things that he said that did not fit were 'lies.'
Right now, somebody in NZ or overseas could be using a computer programme to reconstruct Robin's death, that was the job of the NZ Police, but at some point the truth became something those particular Dunedin officers didn't want to know.
No comments:
Post a Comment