Presentation on theme: "Svend Richter Faculty of Odontology, University of Iceland CONCLUSION, PROBABILITIES AND FINAL COMPARISON REPORT 8 th International course."— Presentation transcript:
Svend Richter Faculty of Odontology, University of Iceland CONCLUSION, PROBABILITIES AND FINAL COMPARISON REPORT firstname.lastname@example.org 8 th International course in Forensic Odontology, Oslo, Norway June-July 2010
PM Comparison AM Restorations Missing teeth PM AM Missing teeth PM AM PM Root canal fylling DNA
- knowledge and experience Conclusion based on probabilities
INCONSISTENCIES When comparing AM and PM records, there are frequent discrepancies or inconsistencies. These may be explainable and thus compatible with identification. If not, identity has to be excluded
Compatible inconsistencies Frequently due to charting errors e.g. where molar or premolar has been extracted and the space is closed Restoration recorded PM being present on a second premolar may be charted as present AM on the first premolar. This is simply a misinterpretation of which tooth was extracted
Compatible inconsistencies Teeth absent PM but present AM, suggest the victim later may have visited another dentist. The same applies to restorations and root canal fillings found PM but not present AM
Incompatible inconsistencies No explanation can be offered for the discrepancy Typical incompatible inconsistencies AM radiographPM radiograph Missing tooth in adultTooth present RestorationVirgin tooth Fully formed toothIncomplete formed tooth Severe vertical alveolar bone lossNormal bone height Root canal fillingNo root canal filling
Unexplanable discrepancies? PM x-ray confirm DO restoration in 14. If AM x-ray shows MO restoration you have the wrong guy. In case of no AM x-rays it can be a charting error in the dental record and if other details prove to be the same you can exclude this tooth from the comparison. In this actual case that was the reality
Unexplanable discrepancies? Distal restoration in 23 may have been placed earlier or later by another dentist that made the dental record, which the AM registration is based on
Unexplanable discrepancies? 11 and 21 are missing PM in this case and therefore no information about the restorations
PROBABILITIES The adult dentition has thirty two teeth with 160 surfaces. The innumerable combinations of missing teeth, carious lesions and restorations form the basis for dental identification
Morphology of individual restorations, features within root canals, periapical and surrounding bone further add to the characterization
COMBINATIONS 148 SURFACES If 20 surfaces has restorations, the possibilities are 2,7 x 10 24 which surfaces are filled
COMBINATION OF MISSING TEETH Number of teethNumber of combinationTeeth present missing132 1 31 249630 34.96029 435.96028 5201.37627 6906.19226 73.365.85625 810.518.30024 928.048.80023 1064.512.24022 11129.024.48021 12225.792.84020 13347.435.60019 14471.435.60018 15565.722.72017 16601.080.39016 Of course teeth are not lost at random and that is also true for filled surfaces. We would welcome scientific data on frequencies. Preferably would we like to have such data for most details in different age group, sex and different population?
If restorations and missing teeth are not interrelated, the joint frequency of two details is the frequency of the first muliplied with the second If one adds a third, the joint frequency would be the joint frequency of the two multiplied with the frequency of the third (Keiser-Nielsen 1977) COMBINATIONS OF MISSING TEETH AND RESTORATIONS Keiser-Nielsen S. Dental identification: certainty V probability. Forensic Sci 1977;9:87-97.
Keiser-Nielsen S. Dental identification: certainty V probability. Forensic Sci 1977;9:87-97. Keiser-Nielsen stated that the probability that one feature exists at the same time as another is the product of probability of each of them: P n = P 1 x P 2 x P 3 x …… P n E.g. if the probability of filling in tooth 14 is 1/10 and the probability of filling in tooth 17 is 1/5, then the probability that both fillings occurs in the same person is: P = 1/10 x 1/5 = 1/50
In lack of epidemiologic data such calculation will never be more than speculation, but thinking along such lines is necessary to be able to get a reasonable conclusion
EVALUATION OF DETAILS The opinion af forensic odontologists will differ what is a detail. Is MOD filling one detail or shall we count surfaces?
One may consider the presence of the same tooth on both records as a detail Another will only consider this a detail if the same restoration is present in both records The third one will give this two points, one for the presence of the tooth and one for the restoration Possibly one will consider this three details for the surfaces and may be one for the presence of the tooth
Keiser-Nielsen (1980) claimed that 12 or more ordinary concordant details would be enough to establish dental identity Identification should be graded as to the weight of dental evidences. ODONTOLOGIC IDENTITY ESTABLISHED 12 or more uncharacteristic concordant details ODONTOLOGIC IDENTITY PROBABLE Between 6 and 12 uncharacteristic concordant details ODONTOLOGIC IDENTITY POSSIBLE 6 or less concordant details
Details are often devided into ordinary and extra- ordinary. Keiser-Nielsen claimed that with extraordinary details, the number may be reduced from 12 to establish identity He considered details extraordinary if they do not occur in more than 10 per cent of all cases
PM AM High certainity in radiographic comparison Few forensic odontologists would question the accuracy of radiographic comparison between AM and PM evidence and less certainty where only dental charts or notes are available
Adams BJ. Establishing personal identification based on specific patterns of missing, filled, and unrestored teeth. J Forensic Sci 2003;48:487-496 Adams used two datasets from a large-scale dental health studies. The first composed of 9.730 US civilians. The second of 19.422 U.S military personnel The results indicate that a definitive number of points of concordance do not need to establish in ID cases. Each case must be assessed individually It was found that even a small number of common dental characteristics may produce a very rare dental pattern
THE COMPARISON REPORT A specific Interpol form The conclusion must be clearly stated so other can understand the basis for it, although dental description have to be given in professional term The report should be signed by two forensic odontologists.
We recommend to write: The conclusion is based on the following concordant details: - 11 fillings: 17,16,14,38,36,35,34,33,43,45,47 - 5 PFM crowns: 13,12,11,11,23 - Four unit PFM bridge: 24,25,26,27 - Root canal fillings: 21,25,27 - 6 missing teeth: 18,15,26,28,37,46 - intact teeth: 32,31,41,42,48