Using Forensic Entomology to establish Post-Mortem Interval

Forensic entomology is 'the use of insects and their arthropod relatives to aid legal investigations'. (Arthropods belong to a group of animals that includes spiders, crabs, scorpions and centipedes, as well as insects).

Forensic entomologists are usually attached to a college or university department, although some will be employed at a museum of natural history.  A forensic entomologist's caseload would not usually justify a position in a forensics laboratory.  Forensic entomology is mainly a sideline to the teaching and research duties of their regular job.

 

There are three major branches of forensic entomology.

 

1. Medico-Legal (Medico-Criminal) Entomology

 

This branch is concerned with the investigation of mainly criminal cases, particularly homicide.  The bulk of the work of the forensic entomologist will involve determining the Post-Mortem Interval (sometimes called 'elapsed time since death') or site of death.  The Post-Mortem Interval is the time between death and the discovery of the body.

Other cases may involve the criminal use of insects, such as when a parent deliberately stings their child with a wasp or bee as a form of punishment.

In cases of unexplained death, where the corpse is too decomposed for the analysis of stomach contents, urine or blood, it is possible to analyse maggots, empty puparia (cases that contained the pupae) or larval skin casts in or on the corpse for evidence of poison.

When investigators need to know the route taken by a car - and there is no GPS navigation device in use or CCTV evidence - a forensic entomologist may be called in to examine the fragmented remains of insects that have become splatted against the windscreen, front fascia and radiator of the vehicle.  Identification of the insect species can provide evidence of the probable passage of the car through a particular area.

2. Urban Entomology

This branch deals with the insects that affect both man and his immediate environment.  The legal proceedings may be heard in either the criminal or civil courts, depending on the case e.g. monetary damages cases will be civil proceedings.

Examples include problems with cockroaches, termites and other pests, insect nuisance from agriculture and neglect cases involving insect infestation of patients in hospitals and care homes.     

3. Stored Product Entomology

This branch is mainly concerned with civil disputes involving insects and other arthropods in food and stored products, but can also include criminal investigations.. 

Different species of arthropods may often be found together in stored containers of illegal drugs.  The drugs are most likely to have been manufactured in one country and sold in others.  If a forensic entomologist identifies the arthropods and then plots their world distribution on a map, any areas of overlap between the species can indicate, approximately, where the drugs might have come from.

Further study of the biology of the identified arthropods may provide information on the surroundings in which the drugs were produced or packed.

Stored Product Entomology also covers cases of fraud where insects have been deliberately introduced into packets of food with the aim of claiming substantial 'compensation'.       

Whilst there are a lot of fascinating cases involving insect evidence - which I can come back to in other blogs - I want to concentrate on the use of forensic entomology to establish the Post-Mortem Interval (PMI), since this is the major area of a forensic entomologist's expertise.

The lure of a decaying corpse

As far as an insect is concerned, a human corpse is a piece of carrion which provides the perfect medium for feeding and reproduction.  Although a wide variety of insects will be attracted to the decaying remains, flies are the most important group from a forensic entomologist's viewpoint.

A forensic entomologist will not need to be called in to assist an investigation until the body is 72 hours or more old.  Up until this point, other forensic methods are either equally or more accurate than insect evidence.  However, after this time, insect evidence may be the only method of determining the PMI.

How to determine the Post-Mortem Interval

There are two methods of determining the PMI.

1) Using Successional Waves of Insects

This method is used when the corpse has been dead between a month and up to a year or more.

During decomposition, the remains go through a variety of biological, chemical and physical changes.  Different stages of the decomposition are attractive to different species of insects.

The first insects to arrive are the blowflies.  They can arrive within 24 hours of death if the season is suitable. 

Other species are not interested in the fresh corpse.  Cheese skippers, a worldwide pest of cheese and bacon, will arrive between 3 - 6 months after death, during protein fermentation.  Beetles that feed on bones will not arrive until the bone is exposed.

Some insects are not attracted to the body itself, but feed on the insects already present.

Ultimately. there will be many species involved at each stage of decomposition.  Each group of insects will overlap with those arriving immediately before and after. 

The forensic entomologist will therefore analyse the groups of insects that are associated with the corpse.  He or she will also need knowledge of the local insect population, as well as knowledge of insect succession and the times of carrion decomposition.

Having all this information in place will allow the forensic entomologist to determine a window of time in which death took place.

2) Using Maggot Age and Development

This method can allegedly give a date of death accurate to a day or less, but more likely a range of days.  It is used in the first few weeks after death.

The theory behind estimating PMI is simple.  Since insects arrive on the body soon after death, by estimating the age of the insects on the corpse, it is possible to estimate the time interval since death.

Maggots are the immature stages of the Diptera or two-winged flies.  The maggots of forensic interest are those of the Blowfly, the first insects to arrive on the dead body.

Here is a  slightly grisly video, explaining the importance of blowfly maggots when estimating the PMI.

As mentioned in the video, each of the developmental stages in the blowfly's life cycle takes a known time.  This is dependent on temperature and available food (not usually a limitation where a corpse is concerned).  Development takes longer in cooler temperatures.

Here is the basic procedure from call-out to a corpse to estimation of the PMI.

1) Collecting, preserving and packing specimens

Samples of insects at all stages of their life cycles are collected from the body, but the maggots are the most important.  Wounds and natural orifices are particularly good collection areas.  Insects should also be collected from clothing, coverings and the surrounding soil, for example.

Some samples should be preserved in 75% alcohol; the remainder should be kept alive for growing on in the laboratory.  Preserving the maggots, etc. allows the entomologist to keep an accurate record of the stage that they were at when they were collected.

Here is a video showing the type of equipment used at crime scenes to collect insects.

The samples are packed in cardboard boxes with a good air supply and taken to the entomology laboratory.

In addition to collecting samples, the forensic entomologist must make extensive notes about the habitat of the death site, take the temperature and humidity at the time of collection and assess the weather conditions.  The elevation and map coordinates of the death site must also be noted.

He or she must also make detailed records about the corpse, such as whether or not clothing was present, was the body buried or covered, depth of burial or covering, location and type of wounds, state of decomposition, how many maggots are present (if any) and whether the body been moved to this site after death.

2) At the entomology laboratory

When the live maggot samples arrive, they will be measured and examined and then placed in a jar with some food, such as beef liver.  The food is placed on top of some sawdust; the maggots will burrow in the sawdust to pupate.

When they pupate, they are taken out of the sawdust and placed on damp filter paper in a petri dish.

The forensic entomologist notes down when pupation occurs and how long it takes.

When the adult emerges it is killed and pinned and placed in an insect box.  The same fate happens to any adult flies collected directly from the corpse.

It is only when the collected eggs or maggots have developed into adults that the forensic entomologist can be absolutely sure which species have/has colonized the corpse.

3) Estimation of PMI

The estimation of PMI is based upon direct age assessment of the oldest specimens developed on the body. 

By relating maggot development to local climatological data from the period prior to the discovery of the corpse, the forensic entomologist can estimate the number of days that it would take for the maggots to reach the size and stage found on the remains.

This time period is the PMI.

Here is a video showing more maggots and pigs carcasses, but it has some good time-lapse photography.

I'll leave you with a video showing 'celebrity' forensic entomologist, Dr Lee Goff, talking about his work. 

Forensic entomology is a huge subject and this blog has only scratched the surface.  I plan to re-visit the subject soon.

Don't forget to leave a comment and a link to your book.















 

 

 

 

 

 



Victim's blood on defendant's clothing - impact spatter or not?

Let us imagine a court scene.  An alleged murderer is on trial.  The prosecution barrister is arguing that the victim's bloodstains on the defendant's clothes are present because  the defendant subjected the victim to a severe beating.  What can the defendant's barrister come up with to counter this assertion?

 

Clearly, the defence barrister wants an innocent explanation for the bloodstains.  For example, the defendant's clothes became bloodstained while he was trying to put the victim into the recovery position.

 

He may be in luck.  An alternative explanation for the amount and distribution of the blood spatter on the defendant's clothing is that the blood originated from the victim's respiratory system i.e. from breathing, coughing or sneezing through a bloody nose or mouth.  

Experiments have shown that an injured victim can produce 'blood aerosols', even if he or she is breathing shallowly through a single nostril or through narrowed jaws, teeth and lips.

The patterns of blood spatter produced by respired 'blood aerosols' can be confused with impact spattered blood.

Here is a very short video showing impact spatter.

Respired blood spatter evidence was pivotal in the eventual acquittal of Sion Jenkins, who spent six years in prison for the murder of his foster daughter, Billie-Jo.

On 15th February 1997, Billie-Jo, 13, was alone at home painting patio doors while Jenkins and his two daughters went shopping.  They lived in Hastings, E. Sussex, in the south of England.

When they returned from their shopping trip, they found Billie-Jo lying in a pool of blood in the back garden.  She had been attacked with an iron tent peg. 

Sion Jenkins became a suspect after 158 microscopic blood spots were found on his clothing.  He was subsequently charged with Billie-Jo's murder.

At his trial in 1998, he was found guilty and sentenced to life imprisonment.

Jenkins has always maintained his innocence.  His first appeal against conviction, in 1999, was a failure but his second was successful.  In August 2004, his conviction was quashed on the grounds that the verdict was unsafe.  He was ordered to be re-tried.

In fact, Jenkins had two re-trials.  The jury were unable to reach a verdict in either re-trial.  After the second re-trial in 2006, Jenkins was officially declared 'not guilty' of Billie-Jo's murder

It was at the re-trials that the respired blood spatter evidence was presented.  Here is a link to an article explaining this evidence.

Blood Spatter Evidence in Sion Jenkins Case

The case remains unresolved.





Killing off your Characters with Chest Injuries

As a crime writer, you know that finding ways to kill off your characters is part and parcel of the plot creation process.  So to help you out, here is a list of chest injuries. 

Although serious, all of these injuries are survivable with timely medical intervention.

So, you can choose whether to keep your readers in suspense while your character's life hangs by a thread; or, maybe, prevent the ambulance from reaching him or her in time.   Whichever way you want to write it, I hope you'll find this list useful for your storylines.

WARNING:  If you are squeamish, you may want to give the videos a miss.

 

Chest Injuries that can kill quickly

 

Windpipe Blockage

If a person's windpipe becomes blocked, oxygen cannot reach their lungs and without treatment, death is rapid.

Windpipe blockage is commonly caused by a person accidentally 'inhaling' a piece of meat.  This results in the so-called 'café coronary', because the symptoms mimic a heart attack.

Another cause of windpipe blockage is an allergic reaction, which causes swelling of the lips, mouth and throat, subsequently preventing air from reaching the lungs.

If a person receives severe blows to the face, their tongue may fall back and block the flow of air to the windpipe.
 

Pneumothorax

Pneumothorax is another name for a collapsed lung.  There are two main types of pneumothorax.

1. Tension Pneumothorax

The lung collapses owing to a stab or bullet wound or even by being penetrated by the end of a broken rib.  As a consequence,  there is a progressive build-up of air in the pleural space, because air leaves the damaged lung but cannot return. (The pleural space is the space between the pleural membranes that surround the lungs and the chest cavity).

The build-up of air causes the heart and the great blood vessels to be pushed to the opposite side of the chest. 

The heart is unable to pump properly so oxygen cannot get to the body's vital organs.  The victim may suffer cardiac arrest because of circulatory instability.

2. Open Pneumothorax

An open pneumothorax  is basically a hole in the chest caused by a stab wound or a bullet.  It is called the 'sucking chest wound'. 

Every time the victim breathes in, air enters the chest cavity through the hole instead of via the windpipe (trachea).  This leads to the victim being unable to ventilate his or her lungs properly and poor oxygenation to the vital organs.

 

Massive Haemothorax

A haemothorax is a condition where blood from torn vessels leaks into the chest cavity.  It can be caused by both blunt and penetrating trauma.  A massive haemothorax is defined as the victim having in excess of 1500ml of blood in the chest cavity.

Clearly, the victim will have difficulty breathing and will be suffering from blood loss, which may lead to shock.

 

Cardiac Tamponade

Cardiac tamponade is where the pericardial sac of the heart is filled with blood owing to blunt force trauma, or a penetrating wound (stab, gunshot) to the anterior chest.

In an uninjured  person, the pericardial sac (or pericardium) is the bag of tissue that surrounds the heart.  The pericardial sac has inner and outer walls which are filled with fluid.  This fluid acts as a lubricant for normal heart movement within the chest.

With an untreated cardiac tamponade, the pericardial sac expands, owing to the extra fluid i.e. the blood, and the heart is squeezed.  It cannot perform as efficiently, so the victim's blood pressure will drop.  The large vessels that carry blood to and from the heart will become obstructed.  The victim will die from cardiac arrest brought about by obstructive shock.

 

Flail Chest

This is a blunt force chest injury.  It is caused when a rib is broken in two places leaving a 'floating' piece of chest wall in between.  In a severe assault, more than one rib would be broken in this way.

This injury results in what is known as 'paradoxical breathing' and the injured chest wall 'flails'.  This is what happens.

On inhalation, the injured chest wall collapses in, whereas the uninjured wall moves out.

On exhalation, the injured chest wall moves out, whereas the uninjured wall moves in.

For the victim, this means that their breathing is uneconomical and the transport of oxygen around the body is hampered.  Furthermore, the underlying lung tissue is likely to be bruised, which also hinders oxygenation.

 

 

Chest Injuries that can take longer to kill

 

Heart Bruise

Here, a patch of cardiac muscle becomes injured as a result of direct blunt force trauma.  The tissue in the region of the impact dies. 

If the affected area is large, then the victim will suffer what is known as 'cardiogenic shock'.  This means that the heart is so damaged that it is unable to pump as much blood as the body needs. 

The condition has a 50 - 75% death rate, even when treated as a medical emergency.
 

Lung Bruise

Lung bruising is also caused by direct blunt force trauma.  Blood and fluid collect within the alveoli (air sacs) of the lungs and prevent oxygen from reaching the blood stream.

If severe, such an injury may not heal for many weeks - if the victim receives medical attention in time.  There is also the possibility that the bruised lung tissue may become hard and, therefore, permanently damaged. 
 

Torn Aorta

The aorta is the largest artery in the body.  It rises from the left ventricle of the heart, forms an arch and then extends down to the abdomen where it divides into two smaller arteries.  The aorta carries oxygenated blood away from the heart.

The aorta may become lacerated as a result of a car accident.  At worst, death will be instantaneous, as the chest cavity fills with blood when the aorta is ripped open.  At best, the tear in the aorta may be small and can be repaired by surgery - assuming a correct diagnosis is made at the hospital.  The victim may be suffering from shock as the result of blood leakage from the tear.

 

Torn Diaphragm

The diaphragm is the sheet of muscle that separates the chest from the abdominal contents.  Injures to the diaphragm can be caused by blunt trauma or penetration.

With blunt trauma, the diaphragm effectively bursts, whereas a penetrating wound may cause small holes in the diaphragm.

Here is a video showing surgery to repair a torn diaphragm.  The injury was sustained as a result of a car accident.

He was a very lucky man, as I'm sure you'll agree.
 



Death by Drowning - Murder, Suicide, Accident or Impossible to Tell?

The mechanism of death by drowning is complex.  Although drowning can be defined as 'suffocation owing to immersion of the nostrils and mouth in a liquid', a drowning person doesn't become asphyxiated simply by suffocation.

 

  
 

 

'Wet' Drowning

 

A conscious person immediately begins to struggle when he or she gets into difficulties in the water.  Every time the person comes to the surface they will try and take a breath and hold their breath when they become submerged again.  Inevitably, they will inhale some water and begin to cough vigorously.  Breathing becomes more difficult and snatched breaths become shorter and shorter.

 

Eventually exhaustion sets in; the person is unable to struggle any more and begins to drown.

 

The drowning person will no longer be able to hold their breath. They will inhale water until they lose consciousness and die.  Death may take 4 - 5 minutes in fresh water and 8 - 12 minutes in sea water.

 

'Dry' or 'Atypical' Drowning

 

People may also die as a result of sudden and unexpected immersion in cold water. 

 

This 'atypical' or 'dry'  drowning' is caused by cardiac arrest owing to 'vagal inhibition'.  This means that the vagal nerve, which lowers the heart rate in a healthy person, is, essentially, overstimulated so that the heart stops beating.  The person suffers almost immediate loss of consciousness and death follows soon afterwards. 

 

The Forensic Pathologist's Problem

 

Drowning cannot be proved by autopsy.  The pathologist has to take into account all the circumstances surrounding the death.  He or she has to prove that the victim was alive when they entered the water and exclude natural, traumatic and toxicological causes of death, before beginning to consider the possibility that the victim drowned. 

 

Here is a link to an article which explains in detail how a pathologist should investigate a possible drowning.

 

The Diagnostics of Drowning

 

So if establishing the fact of drowning is so difficult, can the pathologist determine whether the death was murder, suicide or simply an accident?

Accidental Drowning

The majority of drownings are accidental.  Alcohol intoxication is often a factor - falling into a swimming pool at a party or a solo midnight swim after a few drinks at a holiday beach bar, for example.

In non-alcohol-related accidental drownings, a small child may drown in a shallow garden pond while being left unsupervised or a dare-devil teenager may hit his head while jumping off rocks into the sea and doesn't re-surface alive.

In the absence of any other evidence to contradict a verdict of accidental death by drowning, the pathologist will be able to form his or her opinion accordingly.

Suicidal Drowning

Suicide by drowning is uncommon and difficult to prove without corroborative evidence, such as a suicide note (which must be verified as genuine by a forensic document examiner). 

It is also important to establish whether the victim had a significant history of mental illness.

If a person does decide to take their own life by drowning, the bathtub is the place of choice.  The victim may also have taken an overdose of medication or drunk a lot of alcohol beforehand.

Suicide victims in the bathtub are invariably clothed. 

The pathologist must establish that the nose and mouth of the victim were under water.  When the body is discovered by, for example, the victim's partner, he or she may empty the bathtub or move the body to get the airways clear of the water. 

Consequently, the pathologist cannot be absoutely certain of the original position of the body or the depth of water in the bathtub.

As with all potential findings of drowning, the pathologist must carefully correlate the circumstances preceding the death and the circumstances of the recovery of the victim from the water with the autopsy findings and laboratory analysis.  Only then can the pathologist form an opinion as to the likely case of death.

Homicidal Drowning

Homicidal drowning is actually very rare.  But with all victims that have apparently drowned, the pathologist must establish whether the person was dead or alive before they entered the water.

In other words, did somebody kill the victim first and then fake suicide or an accident or did the person hit their head or suffer a seizure, for example, before entering the water and drowning?

If the victim has injuries to the body, were they inflicted before or after drowning?  Was the cause of death the result of the injuries or the result of drowning?

It is not always possible for a pathologist to form a definite opinion about the cause of death in these instances.

Homicide may be suspected where an adult victim is found drowned in shallow water or when the victim is found naked in the bathtub in a staged 'suicide'.

If a healthy person is pushed into the water and drowns, there will be no evidence of homicide. 

An Unsolved Drowning Mystery:

This blog has barely scratched the surface of this complex topic, but I hope you will find something here to help you with your storylines.

I'm going to finish with a well-known, unsolved drowning mystery, which, perhaps highlights the difficulties that I have alluded to in my blog. 

Hollywood film star Natalie Wood drowned near Santa Catalina Island, California, in 1981.  She had been spending the weekend on a boat with her husband, Robert Wagner, and their friend, Christopher Walken.

At the time, her death was declared an accident by 'drowning and hypothermia'.

In November 2011, the case was re-opened, owing to 'new evidence' having been produced.  As a result of this new investigation, Natalie Wood's cause of death has been re-classified as 'drowning and undetermined factors'

Here is the boat's captain, Dennis Davern's version of events.

Just a cursory online search reveals numerous rumours and gossip surrounding Natalie Wood's death.  Maybe we will never know the truth.  However, the investigation remains open.





 

 

 

 

 



How Familial DNA Searching Could Aid Cold Case Investigations

On 23rd March 1988, Debbie Linsley said goodbye to her parents and drove to Petts Wood railway station with her brother, Gordon. 

Debbie, 26, worked in Edinburgh but had been attending a management course in London. Her parents lived only 15 miles or so from London, so it was a good chance to have a family get-together, particularly as Debbie was going to be a bridesmaid at her brother's wedding in two weeks time.

Gordon dropped off Debbie at the station and she caught the 14.16 Orpington to London Victoria train. 

In those days, many of the train carriages had no corridors.  Instead, they were divided into compartments.  Within each compartment, the seats faced each other along its width and there was a slam door on either side. 

If you were travelling on your own at a quiet time of the day, you ran the risk of being in dubious company at some point in your journey.

Some six minutes away from London Victoria station, Debbie's train stopped at Brixton to pick up passengers.  In that final six minutes between Brixton and London Victoria, Debbie was stabbed eleven times in a frenzied attack.  She put up strong resistance and managed to injure her attacker.  However, she died from a stab wound to the heart.

Debbie's body wasn't discovered until ten minutes after the train arrived at London Victoria.  Her attacker was long gone.  At that time, there was no CCTV to record the passengers leaving the train. 

The police investigation was thorough but the murderer has never been caught.  The murder weapon has also never been recovered. 

But the killer did leave a small sample of his blood at the scene.  Although DNA profiling was not in use in 1988, the case has been subject to periodic reviews.  As a result, the new investigations have taken full advantage of the latest techniques in DNA profiling.  Finally, the scientists were able to generate a full DNA profile of the crime scene blood.

But the killer's DNA profile isn't on the National DNA Database.

Investigators are convinced that Debbie did not know her killer.  They also discount the 'known killer' theory.  This is because a person like Debbie's killer would surely have committed other crimes.  If so, he would more than likely have been arrested for some of them and had a mouth swab taken for DNA profiling. 

Maybe the killer is dead.

But 25 years after Debbie's murder, another cold case review is taking place.  This time the investigators propose using Familial DNA Searching.  Instead of searching the National DNA Database for a profile that matches the crime scene profile, scientists will search for relatives of the offender who may be on the Database.   

One argument for its use is that criminality tends to run in families.  Another argument is that it is a way of keeping the investigation going.

Familial DNA Searching was developed in 2002 by the Forensic Science Service in England.  It is based on the principle that close genetic relatives such as a parent and child or siblings wll have more DNA in common than unrelated persons. 

When a search is made and a number of possible relatives have been identified, further profiling techniques are used to verify or exclude the possibility of relationship with the unidentified offender.

The use  of Familial DNA Searching is controversial, particularly in the United States.  Although openly carried out in California and Colorado, familial searching is banned in Maryland.  Critics describe it as an invasion of privacy or a 'genetic fishing expedition'. 

However, the technique proved effective in identifying a serial killer suspect in California known as the 'Grim Sleeper'.

This is how ABC reported the news of the Grim Sleeper suspect's arrest.

Finally, here is an excellent article detailing successful cases where familial DNA searching has been used, more about the technique itself and the arguments for and against the technique.

Familial Seaching: Extending the Investigative Potential of DNA Typing

Let's hope familial DNA searching proves its worth in the Debbie Linsley case. 









 



What's the Difference between Entrance and Exit Gunshot Wounds?

Firearms account for almost two-thirds of homicides in the United States, so unsurprisingly, gun crime is a popular subject for modern crime fiction. 

 

Ballistics and the forensic examination of firearms are complex topics.  When the crime writer Ruth Rendell was at the height of her popularity, she said she no longer wrote about guns in her novels because she always got something wrong. 

 

I'm sure many crime writers feel the same.  So let's turn the subject on its head and start with the results of firing a gun at somebody.  (We'll look at the forensic aspects of the firearms themselves in future blogs).

 

Gunshot wounds can provide a lot of information about what happened in a shooting, such as the make and model of gun, the range of fire, the sequence of fire patterns, the path travelled between entrance and exit wounds, the likelihood of survival and the specific manner of death.

 

What are the basic features of gunshot wounds?

 

Entrance Wounds

 

• Appear as a punched-out hole in the skin.

• Diameter of the wound is usually smaller than the bullet.  This is because the skin is elastic and it retracts after the bullet enters the skin.

• There is an abrasion ring (sometimes called the abrasion collar) around the wound.  This is a ring of skin with the outer layer or epidermis missing, through which small amounts of blood can escape.

• Underlying tissues will not protrude.

• Tattooing or smudging (gunshot residues) may be present around the wound depending on the distance of the shooter from the victim..

Exit Wounds

 

• Exit wounds from low velocity fireams tend to be relatively small.  They can have a variety of shapes e.g. slit-like, X-shaped, irregular.

• Exit wounds from high velocity firearms tend to be large and destructive. 

• A typical exit wound does not have an abrasion ring.

• Underlying tissues may be protruding.

• Tattooing or smudging is always absent.

Of course, the bullet may not actually exit the body, particularly if the ammunition is low calibre.

A more detailed account of the features of entrance and exit wounds, where the entrance wounds are characterised according to the distance from which the shot was fired, can be found here.

Another difference between entrance and exit wounds concerns bloodspatter.

 

Backspatter is ejected from entrance wounds and travels against the line of fire towards the person firing the gun.  If the shooter and gun are close enough to the victim, this blood may be deposited on the shooter's hands or the firearm itself.  Clearly, there is the potential for good associative evidence here.

 

By contrast, forward spatter is ejected from the exit wound and travels in the same direction as the bullet.

If you are a regular reader of my blog, you'll know that I  wuld normally include a video here, to illustrate what I have been writing about.  However, I couldn't find anything appropriate, so instead here is a gunshot wounds presentation from the Health Training Network.   Although the photographs may be upsetting for some of you, the quality of the information is excellent.  I hope you can find something from it to use in your writing.

I'll come back to this subject in future blogs, but do leave a question if there is something that you particularly want to know about gunshot wounds or firearms forensics and I'll try and help you.

I'd love to know how your writing projects are proceeding.  How close are you to publication?  Maybe you're already a published author.  Why not leave a comment at the end of this blog with a link to your latest book?  

Forensic Botany - an under-used source of potential evidence

Forensic Botany is the application of plant science to the investigation of criminal and civil cases.  The value of using plant remains as evidence lies in the fact that they can be found almost everywhere.

 

But despite its proven value, forensic botany is not part of mainstream forensics.  Its practitioners tend to work in university departments rather than forensics laboratories.

 

A major obstacle to the routine use of botanical evidence has been the lack of trained specialists. 

 

As a degree subject, botany began to wane in popularity in the 1970s. (There were only six of us majoring in botany at my university in 1974).  The courses were viewed as old-fashioned, with their traditional content of plant morphology, anatomy, and systematics.  Instead, students flocked to those courses offering the study of plants at the molecular level.

 

Today, forensic botany encompasses expertise in both traditional plant science and molecular biology.  As well as the interpretation of botanical evidence left at a crime scene, forensic botanists are able to identify individual plants from an analysis of their DNA.

 

So how can forensic botany help an investigation?  Here are a few examples.  The list is not exhaustive, as I am planning on re-visiting this subject in future blogs.

 

• Seeds can be carried in trousers turn-ups (cuffs), thereby potentially linking an individual wth a specific location.

• The identification of vegetable matter in stomach contents can provide evidence of a victim's last meal.

• Pollen types that occur together in a crime scene sample can show where somebody or something has been.  This can be very specific evidence.  It can indicate geographical origin in instances where certain plants only occur in particular areas in certain combinations.


• From the use of plant growth patterns and habitat details, it is possible to infer how long skeletal remains have been present in a particular location.
 
• DNA analysis of fragments of marijuana can establish distribution patterns and links between growers.

Here is a short video that shows how forensic botany can be used to determine that a body has been moved.  The video also shows how a perpetrator can be linked to a scene or victim by plant material.

 

Forensic botany is an important tool for the location of clandestine graves.  Here is an account of a double homicide where pollen evidence helped police find the graves of the victims.

 

On 6th December 1994, Roger Severs was found guilty of the murder of his parents, Derek and Eileen Severs.  He was sentenced to two terms of life imprisonment.

 

Roger Severs was unemployed and lived with his parents at their home in Hambleton, Leicestershire, UK.  One evening, Severs returned home drunk.  His mother was at home, alone.  Severs asked her for money, probably to fund his latest business idea.  When she refused, he flew into a rage and battered her to death with a steak mallet.

 

Later on, when his father came home, Severs beat him to death as well.

 

Derek and Eileen Severs were comfortably off and Roger Severs could expect a good inheritance.  They had been actively involved in their local community and had many friends.  After a week of missed appointments - which was totally out of character - and despite being told by Severs that his parents were on holiday, their friends became increasingly worried and called the police.

 

When the police arrived at the couple's bungalow, they found it in a state of disarray.  In particular, they noticed that the carpets had been removed from two of the rooms.  Severs was adamant that his parents were on holday.

 

However, the police investigations revealed Derek and Eileen had not made any travel arrangements.  Instead, it was clear that they had no intention of going on holiday, as they had made a number of appointments to see friends when they were supposedly away.

 

Two days later, the police arrested Severs and a forensic examination of his parents' bungalow was carried out.

 

Scenes of Crime Officers (SOCOs) found blood spatter in the bathroom, indicating that a violent attack had taken place.  Blood traces near the garage were indicative of a second attack. 

 

The SOCOs also found a trail of yellow fibres with a 'rolled' appearance, suggesting that something heavy had been dragged over the carpet.

 

But where were the bodies? 

 

It was possible that they had been taken to another location.  Derek and Eileen's car was extremely muddy, both inside and out.  The SOCOs took mud samples from the wheel arches and footwells of the car.

 

A detailed analysis of the mud showed that it had been accumulated recently and contained quartz, calcite, ironstone, chert and coated road stone.  A forensic geologist concluded that this mineral composition indicated that the mud had come from an unmade road (trail) in East Leicestershire.

 

A further analysis of the mud revealed several types of pollen grains, in particular, oak, birch and horse chestnut.  The density of the oak pollen suggested that the car had been taken to a site next to an oak tree and also showed the direction in which it had been parked.

 

In order to locate the likely grave site of Derek and Eileen, Professor Tony Brown of Leicester University, a forensic botanist specialising in palynology (pollen analysis), collaborated with ecologists from the Leicestershire and Rutland Wildlife Trust, who possessed good knowledge of the tree species in the surrounding countryside.  Between them, they reduced the search area from a 40km radius to five likely woodlands.  Derek and Eileen's bodies were discovered at the second site that was searched.

Eileen was wrapped in a yellow blanket, hence the trail of yellow fibres found by the SOCOs. 

The soil on top of the bodies came from Derek and Eileen's garden.  Severs had first of all placed the bodies in a shallow dip.  He then drove to and from their bungalow with bags of soil. He emptied the bags on top of the bodies and disguised the grave with leaves and twigs.

The SOCOs found a 'To do' list which Severs had written after the murders.  One of the tasks was to clean the car. Fortunately, he was arrested before he had completed that particular chore.

 

There are lots of interesting cases where plant evidence is important, so, as I mentioned earlier, I'll re-visit this subject in other blogs.  In the meantime, I hope this blog has 'planted' some new ideas that you can use in your writing. 

 

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