I wonder if the name Colin Pitchfork means anything to anyone reading my DNA blog. The possible early release from prison of violent offenders is a hot topic at the moment and although Pitchfork (now aged 66) was originally sentenced to imprisonment for 30 years in 1988, he is still behind bars 38 years after his conviction, and was last denied parole by a review board in 2025.
His crimes? The rape and murder of two schoolgirls, Lynda Mann and Dawn Ashworth, in Leicestershire in the 1980s, plus two other counts of sexual assault on young women, and an attempt to pervert the course of justice.
His crimes? The rape and murder of two schoolgirls, Lynda Mann and Dawn Ashworth, in Leicestershire in the 1980s, plus two other counts of sexual assault on young women, and an attempt to pervert the course of justice.
The real significance of his case? It was the first ever conviction secured on the basis of DNA evidence.
"It wasn't until 2009 that the 'Phantom of Heilbronn' was finally identified - as a woman who worked in a factory that made swabs for DNA testing! Contamination in the production process had been the problem and the police had wasted years on the trail of a non-existent killer. The 'Phantom of Heilbronn' really was a phantom."
He nearly got away with it, for when the police arranged for 9,000 men in the locality between the ages of 16 and 34 to report in and give blood for DNA sampling, he sent along a friend of his with a fake passport purporting to be Pitchfork, a ruse that was only discovered after an overheard conversation in a pub. When Pitchfork finally provided a sample, his DNA was a match for that found on both murdered schoolgirls. Professor (now Sir) Alex Jeffreys of Leicester University was the scientist who helped the police with that investigation and whose pioneering work on techniques for genetic fingerprinting and DNA profiling became standard practice worldwide.
I was intrigued by a book review in New Scientist a couple of months ago. That book is 'The Secrets of Our DNA ' by Turi King. (It's currently on order.) One anecdote in particular intrigued me, so I will share it in full with you:
"In 1993, a 62-year-old woman in Idar-Oberstein in Germany was found strangled. DNA on a coffee cup suggested that two people were present besides the victim, and that one of the apparent killers was a woman. In 2001, the suspected female murderer's DNA turned up again in Germany, this time on the body of a 61-year-old man in Freiburg. Then her DNA started appearing at crime scenes in Austria and France as well.
"In 2007, the mysterious woman hit the headlines when two police officers were shot, one fatally, in their car in the German city of Heilbronn, and her DNA was found in the back seat. This sparked a major hunt for the 'Phantom of Heilbronn' as she became known. But the phantom proved elusive, despite being linked to forty-one crimes via her DNA. In some cases, her accomplices were caught, but they denied that any woman was involved. Police started to consider the possibility that the criminal was transgender.
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| swabbing for human DNA |
While the majority of convictions based on DNA are sound, the example above and a few notable miscarriages of justice mean that DNA 'evidence' has to be interpreted very carefully, as crime scenes are often complex and the process of collecting materials for DNA profiling can give rise to cross-contamination, the unintentional transference of DNA evidence from one item or location to another.
DNA is omnipresent in the animal world. There is no living, reproducing organism that doesn't have DNA as the genome. In fact all animals share some DNA with human beings - probably dating back to the origins of animal life on earth in the hot vents of underwater volcanoes in the planet's oceans.
We know there were various versions of human beings (hominins) back along our evolutionary road, maybe as many as thirteen different types over eight million years since we diverged from chimpanzees (whose DNA is 98.4% identical to human DNA). Nowadays only one exists, Homo sapiens. We know about our ancestors mainly thanks to fossil remains and DNA analysis.
There are also only two types of alligators alive today of the ten species that are known to have existed, from fossil remains and DNA analysis, and one of those, the Chinese alligator, is on the critically endangered list. In the wild, it lives only in about a 5km square region of freshwater ponds in the Anhui province of south-western China. Its close cousin, the American alligator is in much better shape, being widespread though the freshwater wetlands of the southern United States. It is thought that alligators originated in North America some 37 million years ago and that the Chinese branch migrated to Asia across the Bering land bridge some 20 million years ago. They are, of course, the template for the Chinese Dragon of myth and legend.
Why did I want to introduce alligators into this blog about DNA? It's not as though they kill people and need tracking down. That's much more in the nature of crocodiles, who are vicious predators. Alligators by contrast are quite shy and peaceable creatures. No, I had a poem about alligators and thought I might as well use it here.
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| swabbing for alligator DNA |
Alligators
There are two types of alligators.
They are known as
type 1 alligators and type 2 alligators
and it is perfectly possible
to catch either but not both of them.
Type 1 alligators can quite often
be caught during pregnancy
or at birth. DNA might suggest
a pre-disposition for getting caught,
and life for type 1 alligators
is fraught from an early age
which seems particularly unfair.
Type 2 alligators generally
get caught later in life
and it's mostly their own fault
for being somewhat fat and lazy
because it's not as though
they haven't been warned
what might befall them.
As a result of being caught,
both type 1 and type 2 alligators
are awkward customers
prone to spiky, insulting
and moody behaviour and need
careful handling to keep them
from becoming life-threatening.
What? Sorry, my mistake.
I meant diabetes, not alligators.
That makes much more sense.
Thanks for reading, S ;-)

























