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Research Article II

Facing Challenges in Forensic Dental Age Estimations of Adults

Induwara Gooneratne

Sri Lanka Dental Journal 2017; 47(03) 75-79

Induwara Gooneratne Department of Forensic Medicine, University of Peradeniya

IntroductionReferrals for age estimations are common for forensic dental practitioners. Out of many service provisions rendered by forensic dental practitioners to law enforcement agencies and courts, estimation of ages of both young and adults remains high. Among the many instances where age estimations are required, child labour and child employment, sexual abuse or rape, juvenile justice whether general criminal law or special criminal law for children will be applied, issue of birth certificates and passports, assessing general criminal liability or doli incapax, adoption, sponsoring for citizenships, eligibility for parents pensions/widow fund, marriage and of course in identification of the dead are quite frequent. This means that the forensic dental practitioner is entrusted with the estimation of age of an unknown to the nearest accuracy with highest scientific reliability. Certainly, the cases that are referred can include those that are living or dead.

While the approaches for estimating the age of a child or a sub adult is relatively easy, straight forward and reliable, the prediction of the age of an adult whose age is not known is difficult and challenging. Despite the pragmatic difficulties in prediction, forensic practitioners are routinely encountered with age disputes of adults to which a reliable, scientifically valid estimation is expected. With this background in this paper I attempt to review and discuss the evolution of some key dental methods of adult age estimation highlighting their nuances in regard to their

accuracy and challenges. Further, a few cases of adult age estimations carried out by the author are presented evaluating pertinent predicaments faced and highlighting practical perplexities encountered. In the absence of any research published in light of age estimating adults using dental methods in a Sri Lankan forensic set up, this communication lays the foundation for future research and development in this aspect of dentistry.

Chronological Age and Biological AgeChronological age refers to the actual time in years and months a person has been alive. This means the truth of the person’s age. While birth certificates and passports are good documentary evidence to establish one’s chronological age, there have been many instances where these documents have been forged or altered. In other instances, these documents are lost, destroyed or not prepared due to many reasons. In criminal instances, when age is a mitigating factor or an incriminating factor some accused have reportedly destroyed their documentary evidence of chronological age.

Biological age in contrast is ‘how old does he or she seem’ taking into consideration his or her biological parameters. Certainly this is an estimate. What is estimated in a forensic context is the biological age. The actual age or the chronological age of the person is not known to the forensic practitioner and the age of the suspect/victim is estimated using different types of biological data from the particular victim/suspect.

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Two very important assumptions are made here which many tend to ignore. First assumption made is that the biological age and chronological ages are exactly the same or nearly the same. The second assumption is that biologically age of a person can be scientifically estimated to a point estimate – meaning that the age of a person could be given as a year month and date. The truth is far from this. In other words, the biological age that is estimated is merely a statistical estimate which means that there is a standard error, a confidence interval and a standard deviation. In other words it is not possible for the forensic practitioner to provide an exact date of birth for the individual, nor he/she can provide at least an year with one hundred percent accuracy. What can be done is to provide with a rough estimate giving a possible age range. However, the legal fraternity and police expect that the forensic practitioner provides a point estimate of the age of the individual. Of course, this has valid reasons. The law technically says if someone is above a certain age a certain action will or will not apply. For example, in order to decide on a statutory rape when the consent of the woman is not contested, the age of the women is very important – if the woman is above 16 years of age then, there is no statutory rape when consent of the woman has been legally valid. As a consequence, determining the age (when it is unknown) of the woman whether it is 16 or above is technically very important to the court. However, what must be understood by the legal fraternity is that the forensic practitioner provides the opinion based on biological development parameters of the person which may show similar signs between ranges of ages.

Evolving Methods of Adult Age PredictionWhile the estimation approaches used for children or sub adults primarily depends on developmental indicators such as markers of tooth development, bone development or bone fusions, the estimations in respect to adults in contrast are based more on the age changes and degenerative attributions that occur as a natural

phenomena. Notwithstanding the challenges these approaches pose, many researchers have postulated a few key tools to predict the age of an adult. Each of these methods can be broadly classified to main three taxonomies – the methods based on morphological markers, biological markers and the use of radiology.

One of the most popular method which uses morphological characters of teeth in order to estimate age of an adult is the one that was proposed by Gustafson (1950). In this method he and his team evaluated the degree of attrition of enamel, sclerosis of dentine, denticles of the pulp, deposition of cementum and periodontal changes. In effect Gustafson focused on attrition of occlusal or incisal surfaces due to mastication, degree of periodontitis, secondary dentine formation, cementum apposition, root resorption and the level of transparency of roots. Using these multivariate variables he and his team modelled a rank sum equation to be used in predicting age of an adult.

Among the many radiological methods one that was proposed by Kvaal et al ( Kvaal and Solheim 1994) is quite promising. One of the advantages of this method is that the age can be estimated without damaging teeth or their extractions. The tenant that the dental pulp cavity is reduced with the deposition of secondary dentine and the subsequent reduction of the pulp cavity size has been used to theorise this method. Using the radiographs, the pulp length and width - along with root length and width are measured. Kvaal observed significant correlations between different ratios between root and pulp lengths and widths which later have been refined to be used for age estimation purposes of adults. In addition, Kvaal et al included the root transparency lengths in to the model, which later was found to be more promising. The results showed the strongest correlation with the age to be in the ratio between the width of the pulp and the root. This indicates that the rate of deposition of dentine on the mesial and distal walls is

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more closely related to age than that of the roof of the pulp cavity. The use of this method has been popular due to its non-invasiveness and convenience.

Biochemical tests have also been used, regardless of their less popularity. These tests rely on the racemisation of amino acids ( specially aspartic acid) isolated from teeth. Racemisation of amino acid is a first order reaction and is relatively rapid in the living tissues. Aspartic acid has been reported to be with the highest rate of racemisation out of all amino acids and to be stored during ageing. In essence L- Aspartic acids are converted to D Aspartic acids in human enamel, dentine, cementum and they increase with age. The D/L ratios are calculated biochemically and that has been shown to be highly correlated with age of an individual (Ohtani, etal 1997).

A few case StudiesOut of many age estimations that I have conducted over the years for forensic purposes which include both adults and sub adults, below I present four cases with different histories to discuss the methods used and the challenges faced during forensic investigations.

The first case was a female who was referred by authorities for an estimation of age. She was about to get married and unfortunately she did not have a birth certificate or any other document of identity. In the absence of proof to determine whether she had reached the age threshold for marriage according to the marriage law, the authorities have requested a forensic age estimation report. Because she was an abandoned child during her infancy, she has had no clue what so ever to hint regarding her age.

The second was again a female who had wanted to apply for a passport but because her birth has not been registered, she was referred first to obtain a birth certificate after which she was referred to me for a forensic age estimation.

Although the mother of the woman was living, she ( the mother) has only a vague recollection of the year she was born. According to the history, this woman was the third in the family of six. The two sisters’ who were immediately elder and immediately younger have had their births registered.- so that they had valid birth certificates. In this context, the forensic issue was whether the dental evidence of this woman are compatible with the age she claims.

The third one was an elderly man who was due to retire from service. Apparently there has been a petition against him that he has forged his identifications and age indications so that he could work longer in the service. Having found some evidence that revealed his ‘natural’ birth date, which, by the way was five years higher than what he claims now as his age. The forensic question at stake in this case was to determine scientifically which could be the actual age of this man - the one he claims now or the one which the complainant allerges which is five years older?

The next case is a skeleton remains referred for post mortem examination. Out of many age estimations I have conducted at post mortem, this case is presented to illustrate the differential approaches a forensic practitioner can make when the cases are referred at post-mortem. The skeleton remains were found by the police in Ampara district and the court requests the identity of the victim and the cause of death. In the routine process of post mortem examination for identity, the estimation of age is one that is critically important. Due to the fact that the teeth of the victim can be taken out for further investigations, at post mortem, a forensic practitioner can perform additional investigations other than that were done if he/she were living.

As a routine practice, after having taken the relevant history, I would carefully observe external features and intra oral features as

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indicators of age. For live cases (for above cases one to three) I used Kvaal and Solheim method due to its un-invasiveness while for post-mortem cases( above fourth case) I used Gustafson method coupled with Lamindin’s approach to ascertain the age.

Facing ChallengesCertainly, estimating the age of an adult using any method is difficult. Each method has its own inherent merits and demerits. Given the unavailability of any other reliable method available other than dental methods for a forensic pathologist to estimate the age of a living adult, the opinion of the forensic dental practitioner becomes critical. For this reason, many forensic pathologists rely on the opinion of the forensic dental practitioner for an age estimation using dental parameters. However, there is no shortage of disagreements on the dental methods of age estimation of the adult. Much of criticisms have arisen on the methods proposed due to the asserted subjectivity of the variables measured. What several opponents suggest is that, although the variables studied for example the level of attrition in Gustafson method or root translucency in the Kvaal method are quantitative on the surface, they are in fact qualitative given the nature of imminent inter and intra examiner variation. But, in the absence of these methods, there is no other scientifically reliable method to opine in regard to an adult age. The question then is, whether practitioners abstain from providing an opinion because it has some valid criticisms or rather provide an informed opinion to the court indicating in the report the purported merits and demerits of the opinion so that the court then can weigh in the reliability of the opinion and decide on adducing. On the one hand, these models postulated either Kvaal, Gustafson or Laminden though are statistically significant for the samples used, their test statistics for example R, Standard Deviations, coefficient of variance, standard error (SEE) are considerably high, which means that the estimated age can only be given as

a long range. In this situation, whether these approaches are really useful for court purpose is a question. The courts of course anticipate a point estimate which means that the practitioner is expected to provide at least the year as the age. For example in a case where the date of birth is sought in order to prepare a birth certificate, and the estimated age in fact ranges between eight years – would this opinion serve any purpose for the victim or courts? On the contrary with the nature of the scientific findings, the practitioner is not in a position to pinpoint a point estimate – if one does, it can be scientifically flawed given the range of standard deviations, R or SEE in the models computed.

Further, the original studies have been carried out using western or foreign populations and their applicability to local populations are unknown. In the literature many have indicated that even in the same populations there can be variations observed in dental age indicators not due to age changes but due to other confounders for example nutritional, habits and other confounding factors. Next is the documented inter and intra examiner variations that can occur in measuring some of the ‘qualitative like’ indicators such as attrition and root translucency. While these variations can exist, their significance in the model to predict the age is unarguable. Moreover, according to national health survey a large proportion of our elderly population is edentulous or partially edentulous or their DMFT values are significantly high. At many times when referrals are made for dental age estimation, it has been a concern that the target teeth are missing – in which case it is not possible to opine on the dental age. Finally it is important to consider the discrepancy that can exist between chronological age (which the court anticipate) and the biological age that is calculated using biological/dental markers.

ConclusionDespite the practical difficulties one may encounter, estimating an age of an adult for

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forensic purposes is an important service a forensic dental practitioner can provide. The literature indicates a few relatively reliable methods to estimate the age of adult using dental variables. However, these methods are not short of criticisms or de-merits inherent to them. In the absence of any other reliable method that can be used to estimate the age of an adult, the significance of the dental approach remains high. Notwithstanding the criticisms one can present on dental approaches, the practitioner has to be aware of the statistical limitations and the importance of these in interpreting the results in order to further qualify the opinion. Perhaps, it is always better that the forensic practitioner informs the court the merits and the de-merits of the method used and the inability of the available science to opine on a point estimate, so that the court can use the opinion rendered in a manner suitable to solve the legal issue at their hand.

References

1. Gustafson G (1950) Age Determination from Teeth. J of Am. Dent. Assoc. 41: 45-54

2. Kvaal S and Solheim T ( 1994) A non destructive dental method for age estimation. J of Forensic Odontostomotol.12(1) 6-11

3. Ohtani S and Yamamoto K (1991) Age estimation using the racemisation of the aspartic acid in human dentin. L of Legal Medicine 41. 181-190

4. Gooneratne I (2016) Chronological ages and their importance to Law and Forensic Practice in Sri Lanka. SLJFMS 8 (1) 14-20

5. Dalitz G D (1982) Age determination of adult human remains by teeth examination. J of Forensic Sci. soc.3: 11-21

Facing Challenges in Forensic Dental Age Estimations of Adults