Svend RichterFaculty of Odontology, University of Iceland

CONCLUSION, PROBABILITIESAND FINAL

COMPARISON REPORT

svend@hi.is

8th International course in Forensic Odontology, Oslo, Norway June-July 2010

PM

Comparison

AM

Restorations Restorations

Missing teeth

PM

PM

AM

Missing teeth

PM AMPM

Root canal

fylling

Root canal

fylling

DNA 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 inconsistenciesAM radiograph PM radiographMissing tooth in adult Tooth presentRestoration Virgin toothFully formed tooth Incomplete formed toothSevere vertical alveolar bone loss Normal bone heightRoot canal filling No 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

PROBABILITIESThe 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 1024

which surfaces are filled

COMBINATION OF MISSING TEETHNumber of teeth Number of combination Teeth present

missing 1 321 32 312 496 303 4.960 294 35.960 285 201.376 276 906.192 267 3.365.856 258 10.518.300 249 28.048.800 23

10 64.512.240 2211 129.024.480 2112 225.792.840 2013 347.435.600 1914 471.435.600 1815 565.722.720 1716 601.080.390 16

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:

Pn = P1 x P2 x P3 x …… Pn

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 ESTABLISHED12 or more uncharacteristic concordant details

ODONTOLOGIC IDENTITY PROBABLEBetween 6 and 12 uncharacteristic concordant details

ODONTOLOGIC IDENTITY POSSIBLE6 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

ORDINARY VS EXTRAORDINARY DETAILS

ORDINARY VS EXTRAORDINARY DETAILS

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

COMPARISONREPORT

VICTIM IDENTIFICATION

REPORT

VICTIM IDENTIFICATION REPORT

ORIGINAL VICTIM IDENTIFICATION

REPORT

Thank you!Thank you!

Questions?Questions?