Mathematics of Tsunami Identifications (paper)
"Closed" vs. "Open" Disaster: Useful distinction or misunderstanding?
Identifying whole families by DNA
WTC identification strategy
Progress on WTC identifications
Re-uniting El Salvador families
Forensic mathematics home page
Charles Brenner, Ph.D.
January 8, 2005 There are many news stories about plans to identify the tsunami victims, using DNA of course.
My initial reaction to the disaster was that an extensive DNA identification effort would be unlikely. Several reasons:
I was in Thailand last week to give advice on DNA identifications. I am participating in two ways:
As it happens, DNA is unusual as an identification modality that naturally and customarily lends itself to a numerical expression. The strength of a DNA match is expressed by a number, the likelihood ratio, such as 1 billion, whereas a dental or fingerprint ID is expressed by an adjective, such as "positive" ID meaning in effect that the likelihood ratio is essentially infinite.
From my perspective the lack of an overall quantitative framework in which ID's are defined is unfortunate and awkward. Why? Because some of the incidental data, such as the geographical location where a body turned up, also reasonably lends itself to expression as a number.
Exercise: probability of ID with only DNA10000 missing => prior odds=1/10000
posterior odds = LR prior odds = 200000/10000 = 20:1
probability = odds / (odds+1) = 95% certainty of identity;
Exercise: probability of ID with DNA and extra information10000 missing => prior odds=1/10000
"physical attributes LR"=10
DNA LR = 200000
posterior odds = LR prior odds = (5010200000)/10000 = 10000:1
probability = odds / (odds+1) = 99.99%. confident identification
However, if the beach where the body was found limits the number of possible identities 50-fold, and if gross physical attributes reduce it 10-fold further, 1 million may be sufficient.
Perhaps this unfortunate situation is an inevitable consequence of the lag in DNA profiles coming forth. After all, it might be possible to consider dental and fingerprint evidence from within a quantitative framework in principle while in practice never using it, but such an arrangement is obviously artificial.
And to be sure the problem is a little academic.
We will know more in a few weeks.
Do not Ignore Nails as a Sampling Option for Victim’s DNA Source in Mass Disasters
Most reports describing sampling from victims of the tsunami
For more information and your input, contact Cristián Orrego — cristian (dot) orrego (circle-a) doj.ca.gov
2. Oz C, Zamir A. 2000. An evaluation of the relevance of routine DNA typing of fingernail clippings for forensic casework. J. Forensic Sci., 45(1): 158-160
3. Tahir MA, Balraj E, Luke L, Gilbert T, Hamby JE, Amjad M. 2000. DNA Typing of Samples for Polymarker, DQA1, and Nine STR Loci from a Human Body Exhumed After 27 Years. J. Forensic Sci., 45 (4): 902-907
4. Nakanishi A, Moriya F, Hashimoto Y. 2003. Effects of environmental conditions to which nails are exposed on DNA analysis of them. Legal Medicine 5 (Supplement 1): S194-S197
Fujita Y, Kubo S, Tokunaga I, Kitamura O, Gotodha T., Ishigami A.
2004. Influence of post-mortem changes
on DNA typing (D1S80, THO1, HLA DQA 1, and PM typing system): case studies for personal identification. Leg Med (
As I have mentioned before, I don't think the practice of mass disaster identification is yet a mature science. There are methods but not methodology, guidelines but not rules, a lot still to be experienced. Here are my opinions about identifying the bodies from the tsunami.
But I'll set those problems aside, not because they are not interesting, and not because other problems are necessarily even greater, but simply because they are outside my expertise.
Even so, the size of the individual disasters is staggering.
For the tourists, direct references may often be available in the form of intimate items left at home like toothbrushes, but often not. People carry those things when they travel. Where people's homes or hotel rooms were demolished, their personal relics are gone or at least unattributable. Therefore identification by direct reference figures to be spotty.
Nonetheless in principle there is a chance to identify such a family if it is found. If the bodies can be shown by DNA to be related in a certain way, and if no other family in the vicinity has the same family tree, then we would know who they are. I don't think this outcome is going to happen very often though.
DECAY CHALLENGES FORENSIC SKILLS "In the tsunami disaster, however, the rapid decomposition is a unique problem"