1. The Story of Sally Clark
Group 2 - Jing Kai (Presenter), Nabilah, Soon Guan
Famous story regarding false accusation of murder and miscarriage of justice

2. Reading
Sally Clark (5 February 2017). Retrieved 21 March 2017, from
The statement by Professor Dawidon: SALLY CLARK APPEAL. Retrieved from
The first reading is a web page depicting the story of Kelly Clark
The second reading is the report regarding the appeal for Sally Clark’s conviction

3. Overview Background Information Conviction for Murder
Analysis of Statistical Evidence
Aftermath
Conclusion

4. 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)

5. 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
-Presence of the bacterium staphylococcus aureus in multiple sites including his cerebro-spinal fluid, indicating baby could have died due to health causes.
-Conclusion based on Bayes analysis that since this probability is very low, the probability of murder is very high

6. The Antagonists 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!
Dr Alan Williams
Along with the evidence (or lack thereof) presented, two other factors resulted in Clark’s miscarriage of justice. One of them is the withholding of...

7. 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
The other is the statistical analysis done by Prof Roy Meadow, Professor of paediatrics at University of Leeds
Based on medical knowledge and general observation of trends, he deduced using Bayes analysis that there is a 1 in 73 million of double cot death. Calculated by assuming both cases of cot death are independent. This is a highly flawed analysis and we will look into this subsequently

8. Analysis of Statistical Evidence
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
Done by Prof Philip Dawid from the Royal Statistical Society, as mentioned in the second reading
Previous statistical study focused on 3 pre-natal factors in families: Smokers, no waged income and mother aged below 27 at second birth. Didn’t investigate into these other variables which would affect the overall rates.
Eg. Males have higher risk, 1st cot death can indicate risk of genetic predisposition and increase the risk of second child dying from cot death
Backed up by extensive SID stats for England

9. Analysis of Statistical Evidence
2) Relevance of data:
Fallacious logic
Probability of double cot death Probably of innocence! (Prosecutor’s fallacy)
Double cot murder is a less likely phenomenon
Relative likelihood should be used
Concentrates on murder as a single causation if death is not caused by SIDS. But in reality, there are many other causes up for consideration.

10. Relative likelihood
P (2 murdered babies in a family) = 1 in 15 million
P (2 SIDS deaths in a family) = 1 in 5 million
P (2 SIDS deaths in a family) : P (2 murdered babies in a family) = 3 : 1
Not the real values, just illustrated as an example. But statistically speaking, it is far more unlikely for a double murder

11. 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
Along with the help of divorce lawyer Marilyn Stowe, as they felt something fishy about the case

12. 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 post- traumatic disorder and alcohol dependency syndrome → Passed away on 16th March 2007 due to acute alcohol intoxication
As the nature of her conviction as a child-killer, and her background as a solicitor and daughter of a police officer made her a target for other prisoners.

13. Dr Sam Gulino, forensic pathologist for the State of Florida, USA.
"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.
Shows that the usage of statistics in the entire conviction process was highly screwed up

14. Conclusion
Logical and accurate use of statistical information with explanations required
Data needs to be precise and context- specific
Failure to make appropriate inferences from statistics can result in fatal consequences
This is a perfect example of statistics used wrongly.
Logic can be counter intuitive sometimes, so care has to be taken

15. Thank You!