Recommendations for the forensic diagnosis of sex and age from skeletons
Introduction
We present here recommendations from a large group of practising forensic anthropologists since they may be useful for other practitioners. It is a comprehensive review of existing methods, evaluated for their practical use.
In the last few years, the number of works aimed at standardising, professionalising and institutionalising various aspects of forensic activity has increased rapidly. An important element of those works is their practical recommendations, which at the same time help to establish whether issued opinions have been drawn according to rules of the profession (lege artis). The series began with recommendations for forensic chemistry (Bonte et al., 1997). The next was the first classical work, which concerned identification based on images (Other-Ref: Buhmann et al., 1999a, Other-Ref: Buhmann et al., 1999b, Other-Ref: Buhmann et al., 1999c, Other-Ref: Buhmann et al., 1999d, Other-Ref: Buhmann et al., 1999e), followed by recommendations for age diagnoses in living individuals without documentary proof of age (Schmeling et al., 2001a, Schmeling et al., 2001b, Schmeling et al., 2001c, Schmeling et al., 2001d, Schmeling et al., 2001e, Schmeling et al., 2001f, Schmeling et al., 2001g, Schmeling et al., 2001h, Schmeling et al., 2001i, Schmeling et al., 2003; Ritz-Timme et al., 2002; Lockemann et al., 2004). The present recommendations, drawn up by the study group on forensic age diagnostics (AGFAD, Arbeitsgruppe Forensische Altersdiagnostik) of the German Society of Legal Medicine (DGRM, Deutsche Gesellschaft für Rechtsmedizin), are a further link in that chain. A major precursor was recommendations for historic skeletons (Ferembach et al., 1979).
The present recommendations differ from the existing AGFAD proposals in as much as they include the diagnosis of sex. This is necessary for practical as well as for logical reasons: the age of a skeleton is always determined in conjunction with its sex; and the two diagnoses are mutually dependent. There are sex-related age indicators and age-related sex indicators.
For more detailed literature on sex and age diagnostics, the following overviews are recommended (in order of importance): Krogman and Işcan (1986); Knussmann (1988); Saunders and Katzenberg (1992) and Kemkes-Grottenthaler (2002). There are, in addition, many other method guidelines, but caution is advised when applying them. Reference should always be made to trusted monographic reviews and, above all, to the original literature, before making a diagnosis. This article is not intended as a manual, but recommends directions and procedures, consequently not all relevant literature is quoted. These recommendations may also be used for evaluations, including quality checks in court.
Section snippets
Preparatory work
Initially, an assessment of the individuality of the skeletal elements studied should be carried out, that is a check to see if all the skeletal parts belong to the same individual. Criteria to be used include joint articulation and fit at fracture edges, appearance of muscle attachments and size indicators (Rösing and Pischtschan, 1995; Ubelaker, 2002). Moreover, molecular biological polymorphisms may be used in special cases and for the purpose of cross-checking and confirming results.
In
Sex
The numerous available methods can easily be divided into those that are less work-intensive thus giving results rapidly, but showing high error rates, and those that require greater effort and more sophisticated equipment, but are more reliable. Based on this division, a two-stage approach is recommended. The first stage is to apply simple field methods; the second stage is to draw on sophisticated laboratory methods. In the case of the present recommendations, simple methods mean
Morphology: sub-adults
In humans most differences between the sexes do not become apparent until after puberty. Morphological methods are therefore less reliable for younger age groups. The distinctiveness of sex-specific features in a skeleton is an indicator for the accuracy of diagnosis. One study even sought to quantify this (Rösing et al., 1995). It follows that molecular biological examination is required more frequently for children. The best available (although not really precise in terms of the statistical
Morphology: adults
The following section deals first with the pelvis, then with the cranium and finally with other regions and methods, based on findings established so far. However, it is worth recalling that biological sex is such an influential and vital a characteristic that it can actually be diagnosed from many other structures, as well.
Molecular biology
The methods of molecular biology render more precise results than morphological assessment. Where subsequent cross-checks have proven possible, the results of blind tests very often match true sex. Moreover, unlike morphological methods, molecular methods are free of the many systematic influences that are often so hard to evaluate. For extraction of short DNA fragments from skeletal remains, experience gained with pre-historic bones may be used (Meyer et al., 2000). However, the advantages are
Age
Methods available for estimating the age of a skeleton can also be divided into two categories: simple but inaccurate methods on the one hand, and complex but accurate methods on the other. The latter include determination of aspartic acid racemisation, bone and tooth histology and the counting of growth layers in dental cement. The simple methods are used as a first stage of examination, whereas the more complex methods are applied in the second stage. The decision whether the second stage
Sub-adults
When examining the remains of children, the method of choice should be the mineralisation status of the teeth. Eruption through the alveolar margin should not be used as an indicator, because it varies considerably. More valuable indicators are the different stages of mineralisation, such as complete development of the crown and root of the tooth.
Liversidge (1993) has defined standard measures for deciduous teeth. With regard to the permanent teeth, it is recommended to use the standards
Adults
The ageing of adults is still a relatively well-founded biological process correlating with time. The indicators of age include the general level of wear (quantifiable in teeth and joints), osteoclasis (well studied for the spongiosa of the epiphyses of the long bones), histological alteration (in teeth and bones), alteration of joints (arthrosis, spondylosis, changes in pubic symphysis), apposition of new material (tooth cement rings) and chemical decomposition (racemisation of aspartic acid).
Conclusions
Methods for examining skeletons in a forensic setting are mainly based on methods originally developed for historical skeletons (but, recent material was often used to develop these methods). In such materials diagnoses can rarely be cross-checked, and there is also less pressure with regard to precision and quantification as compared to forensics. These recommendations are therefore also valid for historical skeletons.
Given the high complexity of sex and age determination, the examiner of an
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