26/08/2013 by All Things AAFS!

Quick Tips: Forensic Entomology – An Introduction.

What is forensic entomology? It is a discipline within forensic sciences where specialists use information that they know about insect lifecycles and behaviours to interpret evidence in a legal context, relating to humans and animals. Entomologists don’t just stick to insects; their work can expand to include other arthropods, mites, spiders and macro-invertebrates.

Insect species which are relevant to forensic entomology

What information can we learn from insect activity? Insects are everywhere and can hardly be avoided, so it’s no surprise that sometimes they get mixed up in the evidence left behind – making them extremely valuable to an investigation. Insects can be a vital part of forensic science as they can provide a time and date to a crime or even a geographical position to where it happened. As some insects only become apparent during certain months, they can become a biological calendar for when a crime might have been committed. As well as being a biological calendar, certain insect species are only native in specific countries or hemispheres. This can be used to create an ‘X marks the spot’ on where a crime was committed – even if a body was moved/buried. Because of this, insects can be the key to past and present events as well as the future.

The insects that are particularly relevant to forensic entomological investigations are blow flies (diptera), flesh flies, cheese skippers, hide and skin beetles, rove beetles and clown beetles. These forensically relevant insects can be placed in four categories:

Necrophages, which feed only on the decomposing tissue of the body or body parts. This is the category that blow flies, hide beetles and clown beetles are classed under.
Predators of the necrophages – for example the rove beetles and ground beetles.
Omnivores that consume both the live insects inhabiting the corpse and the dead flesh – ants and wasps.
Opportunist species, which arrive because the corpse is a part of their local environment. This is where mites, hoverflies, butterflies and occasionally spiders are classified.

Forensic entomologists use the evidence they gain from studying insects within legal cases in either civil or criminal courts. Civil court cases include:

Insect infestation in urban contexts.
Stored product infestations/pests.

Criminal court cases include:

Neglect – either animal or human (elderly and children).
Insect infestation of a body – living or dead.
Death in which foul play is suspected.

This is just an introduction into the world of forensic entomology, if you’d like to know more or further your knowledge on this topic check out this book, I found it very interesting and a terrific read:

Forensic Entomology: An Introduction (UK/Europe)
Forensic Entomology: An Introduction (US/Worldwide Link)
by Dorothy Gennard. Rating – ***
“I used my this for my blog post on the basics of forensic entomology. It is perfect if you’re unsure on whether or not you want to pursue this career/discipline. Definitely a good read if your interest is sparked by Dr Hodgins from ‘Bones’, as it explained everything involved within entomology under legal settings.”

21/08/2013 by All Things AAFS!

Quick Tips: How To Estimate The Chronological Age Of A Human Skeleton – Epiphyseal Closure Method.

This Quick Tips post is the second in the series on age estimation on skeletal remains, if you haven’t read the previous post click here. The previous post provides an overview of the different techniques utilised by archaeologists/anthropologists, which will each be covered in more detail in their own blog post, and the categories that human skeletal remains are placed under according to their chronological age.

One of the methods frequently used by archaeologists/anthropologists to estimate the chronological age of human remains is by studying the level of epiphyseal fusions.

But first what is an epiphysis? An epiphysis is the cap at the end of a long bone that develops from a secondary ossification center. Over the course of adolescence the epiphysis, which is originally separate, will fuse to the diaphysis. The ages of which epiphyseal fusion begins and ends are very well documented, with the majority of epiphyseal activity taking place between the ages of fifteen and twenty-three.

Diagram showing where the epiphysis is found.

As epiphyseal fusions are progressive they are often scored as either being unfused (non-union), united, and fully fused (complete union). Females often experience the union of many osteological elements before males, and every individual experience epiphyseal union at different ages.

Left: Diagram of a skeleton showing the position of the different epiphyseal elements.
Right: A graph displaying the timing of fusion of epiphyses for various for various human osteological elements. The grey horizontal bars depict the period of time, in ages, when the fusion is occurring. All of the data is representative of males, except where it is noted. Data taken from Buikstra & Ubelaker, 1994.

Archaeologists/anthropologists use standards that are well known and documented, such as Buikstra & Ubelaker’s (1994) depicted in the above graph. From the above data we know that, for example, the fusion of the femur head to the lesser trochanter is begins around the age of fifteen and a half and ends around the age of twenty. So if a skeleton has evidence of an unfused femur head/lesser trochanter, there is a possibility of the skeleton having a chronological age of < fifteen years. If there is full union of the epiphyses then the skeleton is more than likely being > twenty years old. But it should be noted that individuals vary in their development so numerous elements should be examined before coming to an accurate conclusion.

Different stages of epiphysis fusion of human tibias. Ages left to right: Newborn, 1.6 years old, six years old, ten years old, twelve years old and eighteen years old.

As several elements of the human skeleton begin the stages of epiphyseal fusion alongside the conclusion of tooth eruption, these two techniques (dentition and epiphyseal closure) are often used complementary to each other to help age sub-adults. The next post in this series on age estimation will focus on the use of dentition to aid with the chronological ageing of human remains.

References:

Buikstra, J.E., Ubelaker, D.H. 1994. Standards for Data Collection From Human Skeletal Remains. Fayetteville, Arkansas: Arkansas Archaeological Survey Report Number 44.

White, T.D., Folkens, P.A. 2005. The Human Bone Manual. San Diego, CA: Academic Press. Pg 360-385.

This is the second of a Quick Tips series on ageing skeletal remains, the next in this series will focus on the dentition method of ageing sub-adults. To read more Quick Tips in the mean time, click here!

To learn about basic fracture types and their characteristics/origins click here!

27/07/2013 by All Things AAFS!

Quick Tips: How can you tell if a skeletal fracture is ante, peri or post-mortem?

There is a relatively easy way to see whether a fracture to a skeleton is ante, peri or even post mortem. It is essential to detail and deduce which category a fracture falls into, as this is very important to see whether the fracture had played a part in the person’s death.

To first classify a fracture, we need to understand what the different categories mean. Some of you will already know these terminology, but here’s a quick reminder;

If a fracture is ante-mortem, it means that the fracture was made before death of the persons.
With peri-mortem fractures, it means that the fracture was received at or near the time of death of the persons – so could have been the fatal strike.
Post-mortem fractures are fractures that have been received after death, so during the time from death to the time of recovery. These fractures are usually from excavation processes, dismemberment, or even natural processes (soil, animal and plant activity).

You will be able to determine if a bone fracture was ante-mortem due to there being signs of healing which is shown by cell regrowth and repair.

With peri-mortem fractures, the person died before the healing started to take place, but the fractures will still contain the biomechanics that are present in ante-mortem fractures.

Post-mortem breaks tend to shatter compared to peri-mortem breaks which splinter, this is because bones which are in the post-mortem stage tend to be dry and rather brittle. Another big indicator of a fracture being post-mortem is the difference in colour.

The ‘Quick Tip’ that my applied anthropology lecturer taught me on how to easily distinguish between peri-mortem and post-mortem is to look at the fracture and decide; is it a clean break, as if you were breaking in half a bar of chocolate? If it is, then the fracture is most likely to be a peri-mortem fracture. If the break looks crumbly, like breaking a biscuit in half, it’s post-mortem fracture. Obviously this tip is not the most scientific, but it’s an easy way to begin your distinguishing process.

Skull with signs of post-mortem fractures. This photo is from a practical lab session.

If you look at the photo above it illustrates a post-mortem fracture. You can determine this easily due to the colour difference on the edge of the fracture, where it is a much lighter colour compared to the rest of the skull and the crumbly nature of the cut.

References:

Most of this is my own knowledge that I learnt during my degree in my anthropology lectures/lab practical sessions. But if you’re looking for a published journal check the one below. It is very informative and easy to understand if you’re a beginner in the world of anthropology/archaeology! It also highlights some problems that can arise when distinguishing trauma, it’s really interesting!

Smith, A.C. 2010. Distinguishing Between Antemortem, Perimortem, and Postmortem Trauma. Academia.edu. Available from here in .pdf form!

19/07/2013 by All Things AAFS!

Quick Tips: The Use of 3D Animation to Visualise a Crime Scene in Forensics.

Many television programs create 3D animations and computer generated images using highly technical computer programmes to help re-enact the scenes or time frame of a crime. This is mostly used so that the viewer at home can really grasp what crime has been committed and help establish a sense that they are a witness. But in reality these animations and images are becoming an increasingly popular technique used within the courtroom.

Information and evidence can be easily constructed from the traditional methods of forensic photography, blood spatter analysis and eye witness testimonies. But in this modern technological time the information gathered is now being used to create computerised animation that depicts the series of events within a crime. But is this method of providing visual appropriate and correct? Could the animation be showing a display of actions/movements that humans can’t possibly and physically make?

There is a big issue with admissibility, which can cause bias. This occurs when the jurors or judge aren’t aware of an error/uncertainty within the procedure of recreating a real life scene into animation. This can cause them to believe that the evidence is a hundred per cent correct, when in fact there are many errors which were created in the process or animation (Ma & Zheng, 2010). Another big problem arises when studies found that people are five times more likely to remember something they see and hear rather than hearing alone. People are also twice as likely to be persuaded if the arguments are backed with visual evidence (Lederer & Solomon, 1997). So this poses a huge problem as false memories and false testimonies could be influenced, which in the end could cause an innocent person to go to jail for a crime they did not commit.

So with the possibility of creating false memories is the use of 3D animation beneficial for the use of visualising crime scenes within court? It is argued that it is as the use of computerised images creates a higher level of accuracy and speeds up the forensic investigational process but only in major crime types, not every day homicides and robberies. However even though it has limited application in the courtrooms, it can pose to be very useful in formal briefs with the forensic personnel, and within the backstage elements of the investigation itself (Ma & Zheng, 2010).

References:

Lederer FI, Solomon SH. 1997. Courtroom technology – an introduction to the onrushing future. Fifth National Court Technology Conference: National Centre for State Courts. Available here.

Ma M, Zheng H. 2010. Virtual Reality and 3D Animation in Forensic Visualization. Journal of Forensic Sciences. 55, 5. 1227-1231.