5 Crime Scene Tips

I don't know if you have come across 'Forensic Magazine' online, but it is a great resource for writers, students, and anybody who wants to know more about forensic science.

 

I particularly like their 'Crime Scene Tips', so I thought I would share some of them with you in this blog.  There's no particular theme, but I hope you find them useful and/or interesting.

 

1. Avoid Contamination

 

A golden rule of crime scene investigation is the control of contamination and cross-contamination.  Here is the link to a list of good practice points:

 

http://www.forensicmag.com/articles/2013/07/control-contamination#.UgoVBnY1jIU

 

Many wasted investigative hours were spent in the so-called 'Spy in a Bag' case owing to contamination.  DNA found on the victim's body was not a significant lead in the case, as the police first thought, but originated from one of the scientists working at the scene.

 

Here are the details:  http://www.standard.co.uk/news/crime/forensic-dna-blunder-hindered-spy-in-bag-investigation-for-a-year-7603447.html

 

2. Finding Evidence Using Fluorescent Light

 

This tip is especially relevant if you are a screen writer. In the link you will find a video demonstrating how to use fluorescent fingerprint powder and specialized lighting conditions to locate evidence.

 

http://www.forensicmag.com/videos/2013/06/find-evidence-using-fluorescent-light#.UgoZwnY1jIU

 

3. How to Process a Fire Scene

 

The destructive nature of fire makes processing the scene very challenging.  Here is the link to the checklists of procedures that fire investigators should follow.

http://www.forensicmag.com/articles/2013/07/processing-fire-or-arson-scene#.Ugo9bnY1jIU

In the UK, Dyson Allen, 19, was recently convicted of the manslaughter of three small children and their elder brother, who tried to rescue them. 

Although Allen maintained that the fire had started accidentally, the forensic scientists who examined the evidence found that it had been started deliberately.

Here is an account of this tragic case:

http://www.bbc.co.uk/news/uk-england-lancashire-23416352 

4. Arson Scene Hazards

This tip is related to no. 3 and should be common sense to experienced investigators, but maybe not to a rookie.

http://www.forensicmag.com/articles/2013/03/arson-scene-hazards#.UgpBc3Y1jIU

5. Documenting a Vehicle Death Scene

Sadly, people die in cars every day, as a result of road traffic accidents.  Inhaling exhaust fumes while inside a car is a common method of suicide,  Perhaps a body is found inside a car on a parking lot and the cause of death is not immediately apparent.

Whatever the situation, here is an account of what the scene examiner should do when processing a car containing a body.

http://www.forensicmag.com/articles/2013/08/documenting-vehicle-death-scene#.UgpEcHY1jIU

Here is a link to a report of suicide in a car in Shanghai, China.

http://www.globaltimes.cn/content/796019.shtml#.UgzpyHY1jI

Thank you for continuing to read my blog.  I'll be back in two weeks time.


 



Asphyxiation - Murder, Suicide or an Accident

When a person is unable to breathe properly, oxygen cannot reach the tissues and organs of their body.  Without prompt medical intervention, their body becomes starved of oxygen and the person dies.  This is asphyxiation. 

 

There are three main categories of asphyxiation:

 

1) Suffocation

 

A person suffocates because oxygen is unable to get to the brain.  Examples of suffocation are drowning, smothering, choking on food and being in a confined space with elevated levels of carbon monoxide e.g. faulty gas fire in a living room.

 

2) Strangulation

 

Strangulation occurs when the blood vessels and airways in the neck become closed. The main causes of strangulation are suicidal hanging and homicidal ligature strangulation, although both causes can be accidental.

 

3) Chemical Asphyxiation

 

Gases such as carbon monoxide or hydrogen sulphide (found in sewers) prevent oxygen from being released to the cells inside the body.  Without oxygen, the cells cannot function and the person dies.

 

I'm going to concentrate on strangulation in this blog.  It is a popular means of killing off characters in crime fiction, but can give you a window of opportunity to save their lives, if your plot demands it.

 

Hanging

 

In the second half of the nineteenth century, a more 'humane' approach to judicial hangings was adopted in the UK. This was achieved by accurately calculating the drop based upon the prisoner's weight.

A prisoner's neck could be broken by allowing them to fall at a pre-determined distance (the drop). The momentum of the drop jerked the head back.  If the knot of the noose was placed to the left of the chin, this would cause the second and third vertebrae to be severed and death would be 'instantaneous'. 

 

If the drop is too short, death is by strangulation.  In some countries with a system of capital punishment, this is the fate of a number of prisoners.  It is usually the fate of the suicide victim also.

 

If a person hangs themselves with little or no drop, they will be strangled slowly.  It is an extremely painful death.  The victim is often found in a kneeling or sitting position.

 

The mechanism of death

• The noose becomes tighter and tighter until the carotid arteries and jugular veins   become closed or 'occluded'.

• The occlusion of these blood vessels causes a severely reduced flow of oxygenated blood to and from the brain.  This is called cerebral hypoxia.

• The weight of the person's body forces the larynx and base of the tongue upwards, so that the person is unable to breathe and is asphyxiated.

Timing of the event

• From 1 - 3 minutes after the person is suspended, they may exhibit signs of physical struggling.

• This is followed by a period of quiet.

• After the person has lost consciousness, the body may exhibit spasms, which are nervous or muscular reflexes.  There will be a final heaving of the chest. 

• Brain death occurs around 6 minutes.

• The heart will stop beating after 10 - 15 minutes.

Appearance of the body

If the carotid arteries are occluded before the jugular veins, the heart will stop rapidly.  The face will be pale and bluish in colour.  There will be no petechiae - small red spots caused by broken capillaries.

If the jugular veins are occluded before the carotid arteries, the face will become engorged and livid (dark red) as the brain becomes filled with blood that has nowhere to go. 

Petechiae will be present inside the mouth and lips  and in the eyelids, where capillaries have broken owing to the excessive pressure.

The tongue may protrude.

Bruising

The rope pressure will cause an inverted 'V' -shaped bruise on the side of the neck.

Here is a link to a scholarly article describing a variety of suicides by hanging. 

WARNING: At the end of the article there are four black and white photos of a body hanging from a tree.

http://www.indmedica.com/journals.php?journalid=11&issueid=131&articleid=1738&action=article

Accidental hangings

Accidental hangings are uncommon.  A young person may be playing with a rope in a tree and somehow manages to become entangled, with tragic consequences.  This happened many years ago to a family member.

Accidental hanging during erotic asphyxiation is occasionally reported in the press.

 

In both instances, the circumstances of the hanging will clearly point to accidental death

Homicidal hanging

Homicidal hanging is very rare indeed and a challenge for the forensic pathologist.  Invariably, other marks will be present on the body that will support the view that the deceased was murdered and did not take their own life.

 

Here is an abstract from a scholarly paper describing such a case.

 

Murder by hanging





Strangulation

 

Strangulation by hand, or by using a scarf, cord or something similar, leaves more evidence on the body than suicidal hanging.

 

Invariably, the murderer will use more force than necessary to kill the victim.  This results in deep bruising, abrasions and contusions on the neck.

 

The victim is likely to be fighting for their life and will struggle vigorously at first.  This will cause damage to the neck, both internally and externally.  For example, the hyoid bone, which lies at the base of the tongue, may be fractured, as a consequence.

 

The victim's face will be congested and livid (dark red) owing to occlusion of the blood vessels.

 

The bruise on the neck from the scarf/cord will be in a straight line and not 'V' - shaped, as in hanging.  There may also be additional bruising at the base of the neck, caused by the pressure of the murder's hand.

 

Strangulation is almost always homicidal.  Accidental strangulation is rare but can occur when a piece of clothing or jewellery becomes entangled in machinery or a moving vehicle, for example.

To finish this blog, here is a link to an article about accidental strangulation which has a happy ending.



Survival from accidental strangulation from a scarf

 

I hope to see you back here in two weeks time.  Thanks for stopping by.