DNA Crime Investigations: Solving Murder and Serious Crime Through DNA and Modern Forensics
196
DNA Crime Investigations: Solving Murder and Serious Crime Through DNA and Modern Forensics
196eBook
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Overview
When geneticist, Professor Alec Jeffreys worked with Leicestershire police on the 1986 case against Colin Pitchfork—the first person convicted of murder based on DNA evidence—a revolution started in the application of forensic expertise. Since then there have been several major cases in which long-standing murders and rapes have been revisited by teams of cold case detectives. Armed with DNA sampling, they have changed the landscape of criminal investigation, as well as the fates of those who thought they could get away with murder, and those who were wrongly convicted.
From initial and intensive DNA lab work to the final serving of justice, true crime historian Stephen Wade examines some of the most high-profile cases of recent years: the controversial suspect in the murder of Rachel Nickell in London; the unsolved slayings of schoolchildren Keith Lyon and Lesley Molseed; the notorious World’s End pub killings; the erroneous charges against the “Cardiff Three”; the fate of Sean Hodgson, subject of one of the greatest miscarriages of justice in English history; and many more.
Product Details
| ISBN-13: | 9781844688142 |
|---|---|
| Publisher: | Pen & Sword Books Limited |
| Publication date: | 02/20/2019 |
| Sold by: | Barnes & Noble |
| Format: | eBook |
| Pages: | 196 |
| Sales rank: | 804,964 |
| File size: | 408 KB |
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CHAPTER 1
DNA in Forensics Explained
DNA exists in a number of our human cells: in the form of genes, it forms the basis of heredity; in form, the genes are arranged in a chromosome, and these are paired, with twenty-three pairs, two of these being the sex chromosomes X and Y (XY in males and XX in females). The DNA is formed in a string of molecules called nitrogenous bases, and there are four such bases that make DNA: Guanine, Cytosine, Thymine and Adenine. As these became more explored and understood, and the nature of DNA described, it was realised that just these four bases exist in the creation of life, and they are arranged along a strand, and referred to by their initials: CTAG.
The DNA helix shape, discovered by Crick and others, is double stranded, and the bases only connect in the pairings of C with G and A with T. In one cell there will be a certain arrangement of these, in the helix shape, and all these together make the genome. When a scientist looks at a profile of the DNA within a cell there will be a string of combinations of pairings, so the strand might have something like this, with two rows of the sets of pairing: one row could be TACGATGC and so on; the other might be ATGCTACG and so on.
In an individual's DNA there will be three billion of these pairings. The notion of 'fingerprinting' with that degree of individuation of the cell's DNA elements make it clear just how specific a test can be when a match between two sources is attempted. But there is even more of a reduction in the actual nature or quantity of the DNA that is used in forensics. This is because there are two versions of DNA: genes and non-encoded. The latter, called junk DNA, is the source of the evidence in forensics. Logically, the DNA in genes per se is clearly functional and part of a larger, complex unity of cells across the living being. But the junk DNA will exist in all kinds of places within the entity.
The double helix, shaped like a twisted ladder (see the first illustration in the plates) has the pairings of A and T and C and G across itself, so the binding is lateral. The sheer astronomical number of cells and of DNA stored can be understood by considering the pairs of chromosomes from mothers and fathers: one chromosome from the mother to each egg made is separate from the others. One egg will have a vast number of combinations of bases, working out at two multiplied by itself twenty-three times. The result is over eight million types of ova. This is then doubled as the same is applied to spermatozoa. Scientists reckon that the resulting possibilities of different DNA in cells is around eight trillion.
We have to ask, what chance has a suspect in the face of this? If a rapist leaves semen at the scene of crime and then the DNA from that is taken and matched to a database, the evidence that he was the rapist is very hard to oppose in a court of law. DNA can be extracted from blood, sweat, semen, saliva, hair and even tears.
Alec Jeffreys in 1984 showed that DNA is polymorphic: that is, sequences of the base pairing of the four bases are repeated in patterns along the section taken from a location. The sequences that repeat are called satellites, and the patterns of repeated strings and pairings are called variable number tandem repeats. In the first years of the application of DNA to forensics, this was the method used, in abbreviation, VNTR. In contrast to this, another type of satellite sequence was identified, patterns that had frequent repeats through a string, and these have become known as STRs-short tandem repeats. The fingerprinting which was first done, when DNA was just being properly understood, was called RFLP – restricted fragment length polymorphism (RFLP). This required a substantial sample for study and it had to be fresh or preserved well. But today, PCR is the method used – polymerase chain reaction (PCR). This uses short repeats and a method of taking out bits of samples at different places along the strand is used to define an established pattern more quickly.
All this is best understood with the help of an image. The process is like watching a factory production belt move along, with a set of objects in each section all designed to go together. Every so often the collection of items will come along, all ready for packing. Then there will be other sequences in between. In the equivalent in DNA, the scientist sees and samples items along the strand to define the individuality of the DNA. This is a summary of the methods:
RFLP
This is still used, but requires the extraction from a good source, then separation and transfer to that sequences may be tagged and then matched according to a pattern. What results from this process is a DNA fingerprint looking rather like a swatch strip showing colours on a band. This is actually a set of bands visualising the DNA pattern using sheets of x-ray film. The resulting strip is an autorad. The line of bands of varying thickness can then be compared to the other sample to look for a match. These patterns of markings are in columns called lanes. Any similarity between the two samples from different locations would be soon identified if they matched.
Polymerase Chain Reaction (PCR)
PCR was used first in 1992, and this shows the repeated strings in a DNA pattern. Amazingly, this needs only a billionth of a gram of DNA material to be studied. The double-stranded patterns in the AT/CG couplings will be in certain permutations, so that in one sample of semen for instance, there could be a sequence with ATGCGCTT and that would be logged and matched. In addition, by denaturing, the two strands can be separated so that they can be seen separately, and this is done by heating to 96 degrees F. Even more impressive is the discovery that the process may be speeded up by 'annealing' bringing out the sequence patterns in a way similar to using predictive texting on a mobile phone.
Short Tandem Repeats (STR)
STR arrived in 1994 and this involves looking at tiny microsatellites in the cell that repeat. The huge advantage here is that this may be used on poor quality samples where some material may have been degraded. Together with PCR, the STR provides a formidable evidential product for the lawyers and police. The combination means that results may be obtained in just a few days. Fragments taken can be separated by a gel electrophoresis, linked to a computer so that a printout can be taken. Another way of presenting the DNA profile is as a graph, similar to that showing heart rate at the end of the hospital bed, or the graph that shows speech utterances in phonetics.
Single Nucleotide Polymorphism
This is the attempt to use just one nuclear base in the study. It involves a search for a designated sequence, much like a security number used in internet banking, where, say, every sixth base is G and every third is T and so on. The search then looks for these sequences. The question then arises about what would be the odds that another person somewhere on earth would have the same sequence and pattern of DNA material? The fact is that such a match to another person would happen in the trillions – as in a sequence of places where a pattern occurs at these numbers in the sequence: 6-9-8-4-3-5-6-2 paired with another eight numbers; the fact is that the inheritance of the DNA patterns at one place in the chain is different from any other place, the possibilities of a match with another person is, as Dr DP Lyle has stated: '12 out of ten billion' unless identical twins, where the DNA is identical.
In more recent cases, the advances have been with dealing with degraded DNA material. This is all about individualising the DNA, and by the side of what used to happen at the beginning of the professional police force, the difference is astronomical. In the 1829 issue of the Police Gazette, for instance, this was the only real method available in attempts to locate a criminal:
Frauds and Aggravated Misdemeanours
A man, about seventy years of age, five feet six or seven inches high, Stout made, hair powdered, full faced, blue undercoat, and wore a dark Shabby greatcoat and white neckcloth, had a respectable appearance, And speaks several languages, carries a black stick and a small square Parcel in oil cloth, and said his name was Lewis ... obtained on false Pretences ... two gold watches, one of which was stamped 'A.S.' ...
The above accounts of the various methods of identifying an individual would have seemed like the most bizarre science fiction to Victorian police. Today, even degraded DNA such as material damaged by heat or decay may be used. SNP analysis will arguably become the norm, as it is most effective in this application as well as in the more mainline tasks.
The final aspect needing explanation is the subject of where DNA is found. Virtually any cellular material left at the scene of a crime may be analysed. Blood, saliva and semen are the most widely used and discussed in press reports, but there are others, and some of these sources mean that different types of DNA are studied. In blood, only white blood cells have DNA, but of course, this presents no problem. It simply means that the white cells have to be separated out from the rest of the sample using a technique where the sample is spun at different speeds to separate out parts of different densities. The red have no nucleus, and so no DNA.
With semen, what happens is that the semen has travelled down the urethra and along the lining of that duct there are cells called epithelial cells, and these have DNA in them. Naturally, some of these cells collect in the semen and so the semen is then usable in analysis. Of course, there is one important point to be made here: this is that in the case of a man who has had a vasectomy operation, because clearly that individual will not have produced sperm, so there would be no DNA, as there has been no sperm moving, that would collect the cells in the urethra.
Again, it is epithelial cells that give the source of the DNA in saliva and in tears. A buccal swab (taken in the mouth) is the most commonly used method of taking cellular material from a suspect. Of course, the advantage here is obvious: saliva and liquid in the tear ducts are acting like a preservative, and the cells there are retained in a tight, easily accessible space, so the sample is very easily taken.
Hair is a rather different proposition. This is because there is no typical junk DNA in the hair strand itself; the DNA is in the follicle at the base of the hair, the root base of growth. Therefore, only hair that has been ripped out by force will have accessible DNA. Naturally, a chunk of hair with follicles, taken from a scalp, will present the analyst with cellular DNA in the materials around the follicles also.
As will be seen in the next chapter on Oetzi, the mummified corpse found in the Alps, DNA in bones is present but is of a different type: this is in cells called osteocytes, and the material there may be accessed many centuries after the death of the entity in question. Teeth, being the most durable constituents of a corpse, provide very useful DNA material. This is due to the long-lasting pulp cells beneath the enamel. Accessing these cells through the enamel can give access to the DNA in the pulp cells, and that can be done many centuries after the death of the individual.
As mentioned in the introduction, with regard to the investigation of the corpse in Dr Crippen's cellar, mitochondrial DNA has its place in this forensic science also; in the mitochondria, the material around the egg, there are tiny molecules within the cells called organelles, and these have mitochondrial DNA. This is passed maternally and can be located in parts of the body which may not have other junk DNA material. As one medical textbook expresses it:
Since mtDNA only undergoes a significant mutation approximately once every 6,500 years it is unchanged over many generations. This means that your mtDNA is virtually identical to your mother's, your great-great-grandmother's and your maternal ancestors' from one thousand years ago. D P Lyle (see Bibliography).
The most famous murder case involving the use of mitochondrial DNA is surely that of the Boston Strangler. When one of his victims' body was exhumed and studied in 2000, semen was found; the source contained mtDNA and the aim was to try to prove that Albert de Salvo, a man assumed to have been the Boston Strangler, was her killer. But he was long dead, so his brother was used as a source of a sample to see if the mtDNA in the body matched his. If it did, then his would be the same as his brother's and so de Salvo would have been confirmed as the killer. But the samples did not match. The Boston Strangler mystery continues as a result of this: not the issue of whether or not specific victims were de Salvo's victims, but whether he was the killer labelled as 'The Boston Strangler' as in both the court process and in the press reports at the time.
As most of the following case studies show, the process of moving from the acquisition of DNA at crime scenes or from individuals in the course of an inquiry is one thing: the use of this in a court of law has been quite another. This stunningly revolutionary new science has had a rough road into the criminal justice system, but the future looks much less bright for offenders, whose DNA will be littered across their trajectory of crime. No more is the standard television image of the villain washing 'clean' the place of a murder something that can be viewed with a sense of outwitting detection. The hoover and the detergents for the floor, together with the white gloves, are no longer enough to give the criminal a sense of security. The dictum that 'every contact leaves a trace' has now gone from what may be found in the grass or in the cracks of concrete to what has been present in a human body in absolutely minute, microcellular condition.
CHAPTER 2From Oetzi to the Garda's National Bureau
On 19 September 1991, the body of a man was found in the Oetzal Alps by two hikers. The figure was lying face down, and in ice. This was a victim of a murder, but one that happened around 3,000 BC. The hikers told the authorities and soon there were scientists on the scene as well as police. The ice had been melting in that valley for a while and, just a few weeks before, two other bodies had been found nearby, but these were two climbers who had died in 1934.
Despite the death being so long before, the finders had still been reckless, not particularly thinking about the work of archaeologists; one man drilled into ice and cut into the iceman's bone. But eventually the body was in a coffin and taken away for analysis. Pictures were taken and then questions were asked about the corpse that was to be named Oetzi. Pollen and dust were analysed; study of his teeth revealed that he had been born near Bolzano but had gone to live in the higher valleys.
It was a murder case and DNA information was to provide the basis for a narrative of Oetzi's life and violent death. There were some obvious features which gave some immediate clues, such as the tattoos on his limbs that suggested some kind of acupuncture treatment, and there was evidence of some damage done to him by a parasite called whipworm. But soon the DNA work gave some results. The mtDNA showed that he was part of a rare group, known in the Alpine region studies as K1. In other words, he was from that area and his people always had been so. He was in his fifties when he died and that means that he was unusually healthy and robust, in spite of the whipworm. His stomach showed that he had eaten a meal not long before death and his clothes were easily imagined from residual traces and fragments. He carried an axe and a flint knife. But he had definitely been in the wars.
Oetzi was holding a knife when he died and he had been shot by an arrow, which caused his death. The shaft had been broken off, and sophisticated x-ray scans showed that he had a deep arterial wound under the collar bone. He had died of a cardiac arrest after blood loss. All this shows a pattern of study involving DNA as well as other methods of analysis, and even in a case from so long ago, there are incredibly minute details of his life and death evident here. The DNA study played a part in this, and we know that he was almost certainly killed.
If all this can be achieved from a 4,000-year-old killing, what can be done regarding murders in the last fifty years or so? In addition to the databases, there are now special units and departments in the police forces of the UK dedicated to this work. In Ireland, for instance, the Garda Cold Case Unit was established in 2008 to work on a number of unsolved murders. The case of Brian McGrath shows the success of this initiative. The news broke in January 2009 that there had been a significant development in the McGrath case: a file has been sent to the DPP with charges made against suspects.
(Continues…)
Excerpted from "DNA Investigations"
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Copyright © 2009 Stephen Wade.
Excerpted by permission of Pen and Sword Books Ltd.
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Table of Contents
Introduction,
Chapter 1 DNA in Forensics Explained,
Chapter 2 From Oetzi to the Garda's National Bureau,
Chapter 3 The Historic Cases: Colin Pitchfork and Robert Melias, 1983-1998,
Chapter 4 The Keith Lyon Case, 1967-2006,
Chapter 5 The World's End Killings, 1977-2008,
Chapter 6 The Lynette White Case and the Cardiff Three, 1988-2003,
Chapter 7 Andrezej Kunowski, 1997-2004,
Chapter 8 Appeals Allowed: Three Cases, 1994-1997,
Chapter 9 The Midlands Ripper, 1993-2000,
Chapter10 By the Old Canal, Ian Lowther, 1977-2000,
Chapter 11 'A Thirty-Six Million to One Chance', Edwin Hopkins, 1995-1997,
Chapter 12 The Lesley Molseed Case, 1975-2007,
Chapter 13 Rachel Nickell and Robert Napper, 1992-2008,
Chapter 14 An Axe Through the Door, Michael Robinson,2000-2004,
Chapter 15 Still Hope - Sixty-Three Years On, 1946-2009,
Chapter 16 Peter Tobin, 1991-2009,
Chapter 17 Trapped after Returning a Knife, Steven Sellars, 1996-2007,
Chapter 18 Closing In: The Death of Colette Arum, 1983-present,
Chapter 19 The Shoe Rapist, 1983-2006,
Chapter 20 Saturday Night Strangler, 1973-2001,
Chapter 21 A Matter of Procedure, 1990-1994,
Chapter 22 Freed After Twenty-Seven Years, Sean Hodgson, 1982-2009,
Chapter 23 Conclusions and Issues,
Bibliography and Sources,
Acknowledgements,
Glossary of Terms,
Index,