Use of prior odds for missing persons identifications

Ranajit Chakraborty,Harrell Gill-King,Bruce Budowle,Jianye Ge

doi:10.1186/2041-2223-2-15

Ranajit Chakraborty, Harrell Gill-King + Show 2 more

Open Access

https://doi.org/10.1186/2041-2223-2-15

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Abstract

Identification of missing persons from mass disasters is based on evaluation of a number of variables and observations regarding the combination of features derived from these variables. DNA typing now is playing a more prominent role in the identification of human remains, and particularly so for highly decomposed and fragmented remains. The strength of genetic associations, by either direct or kinship analyses, is often quantified by calculating a likelihood ratio. The likelihood ratio can be multiplied by prior odds based on nongenetic evidence to calculate the posterior odds, that is, by applying Bayes' Theorem, to arrive at a probability of identity. For the identification of human remains, the path creating the set and intersection of variables that contribute to the prior odds needs to be appreciated and well defined. Other than considering the total number of missing persons, the forensic DNA community has been silent on specifying the elements of prior odds computations. The variables include the number of missing individuals, eyewitness accounts, anthropological features, demographics and other identifying characteristics. The assumptions, supporting data and reasoning that are used to establish a prior probability that will be combined with the genetic data need to be considered and justified. Otherwise, data may be unintentionally or intentionally manipulated to achieve a probability of identity that cannot be supported and can thus misrepresent the uncertainty with associations. The forensic DNA community needs to develop guidelines for objectively computing prior odds.

Highlights

Mass disasters can result from natural, accidental and intentional causes
In situations where the DNA evidence demonstrates that a burial site population does not contain the reported individual, the prior probability of 1/n is rejected; such rejection of an association within a burial site in itself demonstrates a lack of 100% accuracy in an eyewitness account
While the above discussion focuses on the inaccuracy of eyewitness accounts, other assumptions that have been used to contribute to increasing the prior probability can be misleading and/or have been misused in missing persons identifications

Summary

Background

Mass disasters can result from natural, accidental and intentional causes. One of the tragedies of such events is loss of lives. In situations where the DNA evidence demonstrates that a burial site population does not contain the reported individual, the prior probability of 1/n is rejected; such rejection of an association within a burial site in itself demonstrates a lack of 100% accuracy in an eyewitness account. While the above discussion focuses on the inaccuracy of eyewitness accounts, other assumptions that have been used to contribute to increasing the prior probability can be misleading and/or have been misused in missing persons identifications. These include location, open vs closed properties, postmortem interval (PMI) and demographic variables often combined using the product rule. Similar uncertainties are relevant for estimating other anthropometric features on the basis of the skeletal remains of unidentified persons (for example, estimation of stature from skeletal remains [44])

Conclusion

Ballantyne J

17. Drábek J

23. Thompson EA

35. McFeeley P

42. Sakaue K

Findings

44. Peterson HC