Hungry Burglars Beware! Fingerprints Can Be Developed On Food

A number of burglars are unable to resist the temptation to snack on a piece of fruit or chocolate whilst relieving the householders of their more valuable worldly goods. 

 

But rather than taking their apple cores home or eating a whole chocolate bar, many burglars will discard the remains of their snack at the scene  - and leave behind valuable forensic evidence in the form of teeth marks.
 

In Adelaide, a burglary took place in an up-market chocolate factory.  The burglar sampled a few of the products but left the half-eaten bars at the scene.  A forensic odontologist was able to match the teeth marks in the partially-eaten chocolate bars with dental impressions taken from a suspect. 

A quick online search will find many other, similar, examples.

 

In general, food is overlooked as a source of forensic evidence.  However, a perpetrator may handle a piece of food at a crime scene, even if he/she does not eat it.  Consequently, the potential exists for an apple or an orange, for example, to yield fingerprint evidence. 

An item of food may have a porous or non-porous surface, which may be smooth or rough, but it is unlikely to be completely uniform across its surface.  This makes it difficult to choose the best technique for developing fingerprints.

Some techniques are designed specifically to recover fingerprints from porous surfaces, whereas others are designed for non-porous surfaces.  Using the wrong technique may damage the fingerprint and the evidence will be lost.

Until recently, fingerprints had only been recovered from food by scientists from Slovenia and India.  Scientists in the UK were, naturally, interested in these results.  However, the chemicals that were used in the Indian and Slovenian studies are not used to recover fingerprints in the UK.

Scientists at Abertay University in Scotland set out to discover whether they, too, could recover fingerprint evidence from food, but without using the chemicals in the Indian and Slovenian studies.

They started out using conventional UK chemical techniques, but, as expected, the results were disappointing. 

They then turned to Powder Suspension, a thick, tar-like substance that is used to recover fingerprints from the sticky side of adhesive tape.

Here is a video showing how fingerprints can be developed on the sticky sides of duct tape, masking tape and electrical tape.

By modifying the consistency of Powder Suspension and making it more dilute, the Abertay researchers obtained identifiable prints on smooth-skinned fruit and vegetables, including bananas, apples and onions. 

The technique was less successful on potatoes, which are rough-skinned, and eggs, which are porous.

Much more research will need to be carried out before this technique can be used operationally on food at crime scenes.  But, it should give potential burglars something to ponder.  Food for thought, you might say............

Do leave a link to your book/story in the Comments section.  I'd love to read your work.



 

Super-speedy DNA extraction technique is perfect for crime drama

In a single episode of CSI, the featured crimes are solved to everybody's satisfaction and all loose ends are nearly tied.  Those of us with forensic knowledge will probably think 'Yeah, right', but are willing to suspend our disbelief.  It is entertainment, after all.

 

Now, however, solving a crime in an hour may not be so far-fetched after all.

 

 

 

Image courtesy of www.all-about-forensic-science.com

 

 



Engineers at the University of Washington, in collaboration with a company called NanoFacture, have created a device that can extract DNA from body fluids in a matter of minutes.

 

DNA extraction is a complex process, which can take 20 - 30 minutes to complete.  It also requires toxic chemicals, so it is not environmentally friendly.

 

This new extraction technique uses microscopic probes.  First of all, the probes are dipped in the body fluid.  Then an electric field is applied within the fluid.  This causes the DNA molecules to stick to the probes. 

The DNA molecules therefore become trapped on the probe surface.

 

This whole process from body fluid to pure DNA takes only 2-3 minutes.

 

Once the DNA has been extracted, a profile can be generated in the usual way.

 

Here is a link to an article which describes the technique in more detail.

 

New Device Can Extract DNA In Minutes

 

Although the article is slanted more towards medical application of the technique, its potential value in forensic investigations is acknowledged.

 

Here is a (very) short video showing the equipment in use.

 

 

Given that many forensic laboratories have huge DNA analysis backlogs, the time savings on the extraction process could make a considerable difference to throughput.

 

From a crime writer's point of view, this technique offers another way to inject realism into your plotting, but without the need to compromise on reality (unless you want to, of course). 

 

Which forensics techniques do you use in your writing?  Why not let me know in the comments section below; don't forget to include a link to your book or story.

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.