Meadow's law

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Meadow's Law was a precept much in use until recently^[when?] in the field of child protection, specifically by those investigating cases of multiple cot or crib death — SIDS — within a single family.

Contents 1 History 2 Criticisms of Meadow's law 2.1 The prosecutor's fallacy 2.2 Statistical independence 3 References

[edit] History

The 'law' has it that because such deaths are a rare phenomenon and difficult to explain by natural causes, we might say that "One is a tragedy, two is suspicious and three is murder unless there is proof to the contrary."^[1]

The name is derived from the controversial British paediatrician, Roy Meadow, who until 2003 was seen by many^[who?] as his country's leading expert on child abuse. Meadow's reputation went into decline with a series of legal reverses for his theories, and the damage was confirmed in July 2005 when he was struck off the medical register by the General Medical Council for tendering misleading evidence. Meadow's license was reinstated in February 2006 by a London court.

Meadow attributes many unexplained infant deaths to the disorder or condition in mothers called Munchausen Syndrome by Proxy. According to this diagnosis some parents, especially mothers, harm or even kill their children as a means of calling attention to themselves. Its existence has been confirmed by cases where parents have been caught on video surveillance actively harming their children^{[citation needed]}, but its frequency is subject to debate as Meadow claimed to have 'unfortunately' destroyed the original data which he used to substantiate the law ^[2].

As a result of the 1993 trial of Beverley Allitt, a paediatric nurse convicted of killing four children under her care and injuring five others, Meadow's ideas gained ascendancy in British child protection circles, and mothers were convicted of murder on the basis of his expert testimony^{[citation needed]}. Thousands of children^{[citation needed]} were removed from their parents and taken into care or fostered out because they were deemed to be 'at risk'. From 2003, however, the tide of opinion turned: a number of high-profile acquittals cast doubt on the validity both of Munchausen's and 'Meadow's Law'. Several convictions were reversed, and many more came under review.

The only source in the British literature^{[citation needed]} for ‘Meadow’s Law’ is Meadow’s ABC of Child Abuse, the first edition of which appeared in 1989. That was the year the precept was set down in print in the United States by DiMaio and DiMaio, without mention of Meadow. If he borrowed the term from them he makes no acknowledgement.^{[citation needed]} Some have said that we ought properly to speak of ‘the DiMaios’ Law’:

“There have been a small number of reports of more than one SIDS death in a family and of SIDS death in twins. Some of these cases are probably due to random chance. The majority of them, however, probably represent infanticide. It is the general policy of the authors to ascribe the first death in a family presenting as SIDS to SIDS. The second death by the same mother is labeled as undetermined and a more intensive investigation of the circumstances surrounding the death is conducted. … A third such death in the family is felt by the authors to be homicide until proven otherwise.”^[3]

However, Meadow somewhat endorsed the law in his book, ABC of Child Abuse, stating that

'"One sudden infant death is a tragedy, two is suspicious and three is murder until proved otherwise" is a crude aphorism but a sensible working rule for anyone encountering these tragedies.'^[1]

The formula is “clearly fallacious” according to Bob Carpenter, Professor of Medical Statistics at the London School of Hygiene and Tropical Medicine, and expert witness in some of the trials where infant cot deaths were prosecuted as homicides.^[4]

[edit] Criticisms of Meadow's law

Critics of Meadow's law state that it is based on a fundamental misunderstanding of statistics, particularly relating to probability, likelihood, and statistical independence.

At the trial in 1999 of solicitor Sally Clark, accused of murdering her two sons, Meadow testified that the odds against two such deaths happening naturally was 73,000,000:1, a figure which he obtained by squaring the observed ratio of births to cot-deaths in affluent non-smoking families (approximately 8,500:1).

This caused an uproar amongst professional statisticians, whose criticisms were twofold:

[edit] The prosecutor's fallacy

Firstly, Meadow was accused of espousing the so-called prosecutor's fallacy in which the probability of "cause given effect" (i.e. the true likelihood of a suspect's innocence) is confused with that of "effect given cause" (the likelihood that innocence will result in the observed double-cot-death). In reality, these quantities can only be equated when the likelihood of the alternate hypothesis, in this case murder, is close to certainty. Since murder (and especially double murder) is itself a rare event, the probability of Clark's innocence was certainly far greater than Meadow's figure suggested.

[edit] Statistical independence

The second criticism was that Meadow's calculation had assumed that cot deaths within a single family were statistically independent events, governed by a probability common to the entire affluent-non-smoking population. No account had been taken of conditions specific to individual families (such as a hypothesised "cot death gene") which might make some more vulnerable than others. The occurrence of one cot-death makes it likely that such conditions exist, and the probability of subsequent deaths is therefore greater than the group average (estimates are mostly in the region of 1:100).

Some mathematicians^[who?] have estimated that taking both these factors into account, the true odds may have been in the region of 2:1 in favour of Clark's innocence, a far cry from Meadow's 1:73,000,000 against.

[edit] References