| Topic: |
Science > Philosophy |
| User: |
"Sir Frederick" |
| Date: |
20 Aug 2005 10:06:19 AM |
| Object: |
History of Forensic Medicine: On DNA As Evidence |
HISTORY OF FORENSIC MEDICINE: ON DNA AS EVIDENCE
ScienceWeek http://scienceweek.com
The following points are made by Peter Gill (New Engl. J. Med.
2005 352:2669):
1) In 1983, in a village near Leicester, England, a local girl
named Lynda Mann was found raped and murdered. Three years later,
a second girl, Dawn Ashworth, was found dead under similar
circumstances. The similarities between the two cases led the
police to believe that the same person had committed both crimes.
After extensive inquiries, an arrest was made. The suspect
confessed to the murder of Lynda Mann but denied having killed
Dawn Ashworth. Convinced that they had the right man, the police
approached Sir Alec Jeffreys, a professor of genetics at the
University of Leicester, with a request to conduct tests using a
new method that he called "DNA fingerprinting," which had not yet
been used in a real case.
2) The results were surprising: the suspect was exonerated, and
the DNA profiles in the two murder cases were the same,
indicating that a single, unknown person had committed both
crimes. This finding led to the screening of all 5000 men in the
area, using both conventional blood-group methods and DNA
testing. The screening failed to identify a suspect -- because,
as it turned out, the perpetrator, Colin Pitchfork, had paid a
colleague to give a DNA sample in his place. When the colleague
was overheard bragging to a friend about the incident, Pitchfork
was quickly apprehended, analysis of a DNA sample confirmed his
guilt in both murders, and he was duly convicted in 1988.[1]
3) Thus, the first criminal case in which DNA was used provided a
vivid demonstration of the method's potential -- not only for
convicting the guilty but also for exonerating the innocent. It
also demonstrated for the first time that a DNA fingerprint could
be used to find a perpetrator from within a population.
4) In 1985, a year after the development of DNA fingerprinting,
the polymerase chain reaction (PCR) was discovered.[2] The
discovery would revolutionize the field of molecular biology,
though the method would not come into routine use in forensic
cases until the early 1990s, since new platforms and biochemical
tools were needed in order to take full advantage of the
potential of PCR. In particular, new automation technology was
key, and the advent of the automated fluorescent DNA sequencer in
the early 1990s was a major step forward. More generally,
forensic DNA analysis has benefited substantially from the Human
Genome Project, for the genome could be sequenced only with
automated equipment that permitted high-throughput processing.
Because forensic science could use the same equipment and
biochemical tools that gene sequencing used, new methods were
rapidly developed in the early 1990s that would have been
considered impossible just a few years earlier.
5) Perhaps the best example of this adjunct benefit of genomics
was the development of national DNA databases. Since its
inception in 1995, the National DNA Database for England and
Wales has expanded to include more than 2.75 million reference
DNA profiles, against which all specimens obtained from the scene
of a crime ("crime stains") are routinely compared.[3] The
likelihood that a match will be found is approximately 30
percent. Many other countries have since followed suit, and the
benefits of such databases are considerable, since persons who
commit serious crimes such as murder usually have a previous
criminal record. The United Kingdom's policy permits the
collection of DNA profiles from all convicted criminals, as well
as from anyone suspected of committing a crime that could lead to
a prison sentence -- and the law allows authorities to retain the
DNA profile even if the suspect is found innocent. Consequently,
persons who later commit more crimes can be identified and
apprehended quickly.[3-5]
References:
1. Wambaugh J. The blooding. London: Bantam Press, 1989
2. Saiki RK, Scharf S, Faloona F, et al. Enzymatic amplification
of beta-globin genomic sequences and restriction site analysis
for diagnosis of sickle cell anemia. Science 1985;230:1350-1354
3. Werrett D, Pinchin R, Hale R. Problem solving: DNA data
acquisition and analysis. Prof DNA 1998;2:1-6
4. Gill P, Whitaker J, Flaxman C, Brown N, Buckleton J. An
investigation of the rigor of interpretation rules for STRs
derived from less than 100 pg of DNA. Forensic Sci Int
2000;112:17-40
5. Marchi E. Methods developed to identify victims of the World
Trade Center disaster. Am Lab 2004;36:30-36
New Engl. J. Med. http://www.nejm.org
--------------------------------
Related Material:
ON THE NATURAL SCIENCES AND FORENSICS
The following points are made by Jessica Snyder Sachs (citation
below):
1) Anthropologists were the first to cross over from the natural
sciences to forensics. In America, the fateful jump came in the
1930s, when FBI agents setting up the bureau's first crime lab in
Washington, D.C. discovered a whole nest of "bone detectives" in
the red Gothic towers of the Smithsonian Institution, across the
street. As the curators of one of the world's largest collection
of human skeletons, the Smithsonian anthropologists were uniquely
qualified to help the FBI distinguish human from animal remains.
From the identification of bones as human, forensic anthropology
quickly advanced to the identification of individuals, based on
distinguishing bumps and bony scars left by past injuries and the
wear and tear of daily toil (a milkmaid's worn elbow, a tailor's
notched thumb, and a mailbag carrier's crooked spine).
2) But anthropologists quickly realized the near-impossibility of
naming the dead without some method, however crude, of matching
their identity clues to missing person reports for a given span
of time. The most experienced among them could sometimes come up
with a reasonable estimate of time since death by "feel" -- that
admittedly nonscientific second sense based on a lifetime of
processing decayed corpses and crumbling bones. But precious few
ever attempted the monumental task of objectively studying the
stages that mark a human body's passage back to dust. So far, the
most valuable dating method to come out of their research belongs
by all rights to another science.
3) In the i980s, the field of forensic entomology burst on the
scene as if out of nowhere when bug and bone scientists
independently discovered the value of what may be nature's
ultimate postmortem clock -- the cadaver-feeding insect. Maggots,
once routinely washed from the coroner's table with disgust,
suddenly became the hot new thing in homicide investigation.
Still, the extent of the bugs' testimony had yet to be fully
fathomed.
4) As anthropologists and entomologists began teaming up in their
forensic investigations, they naturally turned to a third
specialty to make sense of the roots and vines winding through
their death scenes: A delicate green tendril snaking through a
sun-bleached skull. A tree growing down through a shallow grave
in the woods. A flush of growth marking the outlines of an
inexplicably fertile comer of an abandoned lot. Each became yet
another promising measure of the seasons that follow "death most
foul."
Adapted from: Jessica Snyder Sachs: Corpse: Nature, Forensics,
and the Struggle to Pinpoint Time of Death. Perseus Publishing
2001, p.9. More information at:
http://www.amazon.com/exec/obidos/ASIN/0738207713/scienceweek
ScienceWeek http://scienceweek.com
--
Best,
Frederick Martin McNeill
Poway, California, United States of America
mmcneill@fuzzysys.com
http://www.fuzzysys.com
http://members.cox.net/fmmcneill
*************************
Phrase of the week :
"I would rather do an experiment. That doesn't mean
I think theory is unimportant. It just means I would
rather do an experiment."
-- Costas Spyropoulos (1928-1984)
:-))))Snort!)
*************************
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| User: "Bret Cahill" |
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| Title: Re: History of Forensic Medicine: On DNA As Evidence |
20 Aug 2005 10:30:47 AM |
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Hundreds of U. S. inmates locked up for years were freed with DNA
testing. Extrapolating to the entire prison population indicates
thousands of innocent are still locked up.
A lawyer at University of Houston said of the releases:
"This shows the system is working."
Nope. It shows the exact opposite: science showed the system is NOT
working.
The judiciary did not take into account factors like racism, tough on
crime rhetoric and incompetent defense lawyers.
Bret Cahill
.
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| User: "Day Brown" |
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| Title: Re: History of Forensic Medicine: On DNA As Evidence |
30 Aug 2005 07:43:44 PM |
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Bret Cahill wrote:
Hundreds of U. S. inmates locked up for years were freed with DNA
testing. Extrapolating to the entire prison population indicates
thousands of innocent are still locked up.
A lawyer at University of Houston said of the releases:
"This shows the system is working."
Nope. It shows the exact opposite: science showed the system is NOT
working.
The judiciary did not take into account factors like racism, tough on
crime rhetoric and incompetent defense lawyers.
The locking up of violent thugs, who have numerous incidents that
preclude total innocence, has taken them out of the gene pool, and
as a result, street crime is down.
.
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