The Tanner scale is often used by the prosecution in cases involving the possession, distribution or viewing of indecent images associated with child pornography offences. The principal of the Tanner scale is to define sexual maturity using visual indicators in the development of the pubic and chest areas of a subject individual.
However, the Tanner scale does not place any direct correlation to a subject’s sexual maturity calculated by the scale and the chronological age of the subject. Rather it is recognised that sexual maturity can develop across a wider time span according to a number of factors in a individual which include culture, genetics and hereditary aspects
There is evidence within the paediatric profession of doubts raised as to the accuracy of the scale when deployed to summarise upon the chronological age of a subject. This is published in the following article that highlights such concerns.
|PEDIATRICS Vol. 102 No. 6 December 1998, pp. 1494
Misuse of Tanner Puberty Stages to Estimate Chronological Age
|To the Editor;
One of us has been involved as an expert in several US federal cases of possession of alleged child pornography, in which seized materials (videos, photographs, computer downloads) were used as evidence against individuals identified in “sting” operations, wherein government agents take over pornographic businesses. In these cases the staging of sexual maturation (Tanner stage) has been used not to stage maturation, but to estimate probable chronological age. This is a wholly illegitimate use of Tanner staging: no equations exist estimating age from stage, and even if they did, the degree of unreliability in the staging the independent variable would introduce large errors into the estimation of age, the dependent variable. Furthermore, the unreliability of the stage rating is increased to an unknown degree by improperly performed staging, that is, not at a clinical examination but through non-standardised and, thus, unsuitable photographs.
Therefore, we wish to caution paediatricians and other physicians to refrain from providing “expert” testimony as to chronological age based on Tanner staging, which was designed for estimating development or physiologic age for medical, educational, and sports purposes, in other words, identifying early and late maturers. The method is appropriate for this, provided chronologic age is known. It is not designed for estimating chronologic age and, therefore, not properly used for this purpose.
Arlan L. Rosenbloom, MD
James Tanner, MD, PhD
Pediatrics (ISSN 0031 4005).
Copyright© 1998 by the American Academy of Paediatrics
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