Actually, it’s quite possible to get DNA from a body that has been burnt, depending on the degree of the burning. The amount of DNA recovered may be very small, but there are certain procedures (look up Low Copy Number DNA—incidentally one of the topics for which I applied for my honours thesis in forensics) that can be used for the analysis of these samples. The challenges would be associated with typical Low Copy Number situations (increased stutter peaks, stochastic effects, allele drop-out), as well as mixture interpretation (since the DNA that might be found in saliva is associated with epithelial cells, not the saliva itself—taking a swab of the wound would take epithelials form both the victim and the biter).
Again, DNA collection would be very dependent in the situation.
For example, if the bite was deep and the acceleration used on the body was on the surface, the flame remains on the surface, insulating what’s underneath (hah, I knew I remembered something from the arson lecture of forensic chemistry!) and would protect the material, including transferred DNA.
Also, electrocution shouldn’t cause such a raise in temperature that DNA would be completely degraded. Actually, it’s usually moisture that destroys DNA, not necessarily heat.
For the people wondering how I spend my Wednesday afternoons…
Reblogged from my personal blog. For those looking into being a bloodstain pattern analyst: see all those little scale stickers on the wall? We had to take length and width measurements of ALL OF THOSE STAINS. That came to a total of 126 measurements for the stains alone. This was done to calculate the angle of impact and subsequently determine the area of origin.
Passive: as the name suggests, these patterns have not had an external force. Examples include drips that result from gravity alone, transfer/contact, and pooling.
Altered: the stains have undergone some form of physical or chemical/physiological alteration. Some examples include clotting, insect interference, and dilutions.
Spatter: these stains are the result of an external force acting upon a surface with blood on it. Examples include impact spatter and expirated blood.
Blood flow is a function of blood pressure (and other factors). A vessel that has been completely cut will have less pressure than one that has only been partially cut.
Think about it in the same way as using a hose to water your lawn. If you partially cover the opening with your thumb, the water pressure is higher, thus coming out faster and further compared to an uncovered opening.
Not the most exciting information, but it’s important to get the terminology right. Using the term, “splatter” would look amateur and is actually considered unacceptable by scholars of the field.
In many cases, the entry hole of a bullet (from a handgun, specifically) appears much neater than the exit hole. Entry holes or wounds tend to be round, and if the trajectory was not straight-on, then there may be an abraded side indicating direction of travel. The exit hole would appear torn, with jagged edges; this is mostly due to the loss of kinetic energy after the bullet has passed through something else (for example, the entry side of an object, the muscles and organs of a person).
A bullet that has passed through another object between entering a body will be destabilized by that object. Rifling on pistols give the bullet a spin, thus stabilizing the bullet and keeping it from tumbling in the air. If the bullet has passed through another object (or objects) before hitting a body, the behaviour of the bullet would have changed:
- Since the bullet is no longer stabilized, the aim would be off. A bullet only travels in a perfectly straight line if unimpeded; now that it is destabilized and tumbling, its path is more random. Depending on the impeding effects of the obstructing object(s), the bullet may stray a little or quite a bit from its original path
- The bullet might hit the body when it is not perfectly horizontal (again, due to tumbling). As such, the entry wound would appear more ragged, and at first glance, may look like an exit wound. It should be noted that skin or clothing around the entry would may be “pushed” slightly inward, as characteristic of an entry wound; conversely, the edges of skin or clothing around the exit wound, if there is one, may appear “pushed” outward, following the path of the bullet
In this case, the exit/entry wound may be determined using chemical tests such as the Sodium Rhodizonate test for lead.
This is only true for some cases. A bullet may lose so much kinetic energy that it will not penetrate too deeply into a body, resulting in the opposite effect. It is important to take into account the distance from which the projectile was fired, the distance between the obstructing object and the body, as well as the density and resisting force of the obstructing object.
Changed the theme of this blog. Following will be changes to the format of the content, as well as the tag page and the addition of resource pages.
Anyone want to let me know what they think of the theme thus far?
This blog hasn’t been update for some time, due to my workload.
I’m just letting you know that I will be taking the time after all of my exams have been done to revamp this blog. I’m just not as happy with the content and the layout.
And also, after finishing an intense semester of criminalistics, I have a lot more information to share.
Stay tuned, and thanks for following!