Download Group 2

The Story
of Sally
Clark
Group 2 - Jing Kai
(Presenter), Nabilah,
Soon Guan
Reading
Sally Clark (5 February 2017). Retrieved 21 March 2017, from
http://en.wikipedia.org/wiki/Sally_Clark
The statement by Professor Dawidon: SALLY CLARK APPEAL. Retrieved from
http://www.statslab.cam.ac.uk/~apd/SallyClark_report.doc
Overview
Background Information
Conviction for Murder
Analysis of Statistical Evidence
Aftermath
Conclusion
Background Information
• Born an only child in Wiltshire, South
West England)
• Married solicitor Steve Clark (1990)
• Moved to Cheshire, North West
England in order to practice law with
her husband (1994)
Conviction for Murder
• Two separate incidences where Sally Clark’s baby passed away due to
unknown causes (Sudden Infant Death Syndrome, SIDS)
• Sally Clark was found alone at home on both occasions
• No evidence to prove or disprove her involvement
• Sally Clark was convicted and sentenced to life imprisonment on 9th
November, 1999
The Antagonists
Dr Alan Williams
•
Withheld microbiology test results for
second baby
•
Tests showed the bacterium
Staphylococcus aureus in multiple
sites of the baby → Baby could have
died due to health concerns!
The Antagonists
Professor Sir Roy Meadow
•
Bayes analysis: 1 in 73 million chance
(1/8543) x (1/8543) of two children from
an affluent family suffering cot death
•
Conclusion that since this probability is
very low, the probability of murder is very
high
Analysis of Statistical Evidence
1) Assumption of independence → Flaws in calculation:
•
Lurking variables: Gender, genetic or environmental factors
•
Chances of a second death increases by 5-10 fold after the first
•
Uncertainty with probability of double cot death most likely
understated
Analysis of Statistical Evidence
2) Relevance of data:
•
Fallacious logic
•
Probability of double cot death
(Prosecutor’s fallacy)
•
Double cot murder is a less likely phenomenon
•
Relative likelihood should be used
Probably of innocence!
Relative likelihood
P (2 SIDS deaths in a
family) = 1 in 5 million
P (2 murdered babies in
a family) = 1 in 15
million
P (2 SIDS deaths in a family) : P (2 murdered babies in a family) = 3 : 1
Aftermath
• Unearthing of microbiological tests by Sally Clark’s husband
• Along with the case for flawed statistical evidence, Sally Clark was acquitted
in January 2003
• Review of hundreds other cases → 3 similar cases overturned
Aftermath
• Roy Meadow was struck off the medical register in 2005 for serious
professional misconduct but subsequently reinstated after appeal
• Dr Alan Williams was banned from Home Office pathology work and
coroners' cases for three years
• Sally Clark diagnosed with psychiatric problems associated with posttraumatic disorder and alcohol dependency syndrome → Passed away on
16th March 2007 due to acute alcohol intoxication
"Throughout my review, I was horrified by the shoddy fashion in which these
cases were evaluated. It was clear that sound medical principles were abandoned
in favour of over-simplification, over-interpretation, exclusion of relevant data and,
in several instances, the imagining of non-existent findings."
Dr Sam Gulino, forensic pathologist for the State of Florida, USA.
Conclusion
• Logical and accurate use of statistical
information with explanations required
• Data needs to be precise and contextspecific
• Failure to make appropriate inferences
from statistics can result in fatal
consequences
Thank You!