When previous radiographs are available from a known person, comparison of features between these and radiographs taken from a person of uncertain identity can help in the identification process. Concordance refers to the number of features that match as a fraction of those available for comparison.



(1) number of features that potentially can be matched

(2) number of features not visible on the different sets of films

(3) number of features that match or align


concordance =

= (number of features that match) / ((number of potential features) – (number of features not visible between the sets of films)) * 100%



• minimum score 0

• maximum score 100%

• The higher the score the greater the match.

• Wood et al used >= 80% as evidence for a match in their study of dental findings.


Expanding upon this, I have come up with the following as a tentative scheme.





90 – 99%

close match

80 – 89%


20 – 79%

partial match

< 20%

no match



• There needs to be a minimum number of features available for comparison (potential number minus the available number). The higher the number the greater the confidence there would be in the interpretation. The Student's t-rest can be used to give the true significance for each case.

• Comparison of radiographs would only be valid if the feature being studies was likely to be stable over the intervening period,


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