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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