








































Forensic Anthropology Vol. 2, No. 2: 102–112
DOI: 10.5744/fa.2019.1013

© 2019 University of Florida Press

The USS Oklahoma Identification Project was established to 
attempt identifications for the nearly 400 unaccounted- for 
service members who died during the Japanese attack on 
Pearl Harbor. The analyses and identifications are completed 
by the Defense POW/MIA Accounting Agency (DPAA), with 
DNA analyses by the Armed Forces DNA Identification Lab-
oratory (AFDIL). The mission of the DPAA is to provide the 
fullest possible accounting for missing U.S. personnel. DPAA 
Laboratories are located in Hawai’i, Nebraska, and Ohio.

This unique case report highlights the historical circum-
stances of the Oklahoma loss, including previous attempts 
at identification and the present- day efforts to identify the 
Oklahoma service members, whose remains are heavily 
commingled. The project is presented as a case report to 
highlight the ways in which methods are employed and 
adapted in order to enact individual identifications from a 
large, commingled assemblage. Analytical procedures, the 
sample, extent of commingling, the manner in which identi-
fications are made, and project challenges are discussed.

The Oklahoma project is housed at the DPAA Labora-
tory on Offutt Air Force Base, Nebraska. The project team 
comprises a project lead (anthropologist) and approximately 
10 anthropology analysts, with dental support from DPAA 
dentists and dental hygienists. Work on the project began in 
June 2015.

Historical Background

On 7 December 1941, the USS Oklahoma (BB- 37)1 was hit 
by Japanese torpedoes during the attack on the U.S. Pacific 
Fleet in Pearl Harbor, Territory of Hawai’i (Fig. 1). The hits 
severely damaged the ship, which soon capsized (Fig. 2). The 
casualties, which included 429 individuals (415 U.S. Navy 
personnel and 14 Marines), represent the second- largest in 
the attack, after the USS Arizona.

Recovery efforts began the day following the attack, but 
they were halted on 16 December 1941. Salvage attempts 
began in July 1942 and continued until May 1944; during this 
time remains were also recovered (Harris 2010). The Okla-
homa was decommissioned in September 1944, and while in 
transit to California in 1947 it sank again in the Pacific and 
was not recovered (Naval History and Heritage Command, 
no date). Ultimately, 35 individuals were identified in the 
years immediately following the attack, but the majority of 
the remains were buried as “unknowns” in two cemeteries 
on Oahu, Territory of Hawai’i— Nu’uanu and Halawa (Har-
ris 2010).

Historical Analyses

In 1947, the American Graves Registration Service (AGRS) 
disinterred all Oklahoma unknowns from Nu’uanu and Hal-
awa cemeteries. The remains were transferred to the Central 
Identification Laboratory at Schofield Barracks (Schofield 
CIL) to attempt individual identifications. However, the belief 

1. Following the U.S. Navy hull classification system, BB = battleship, 
37 = hull number. Navy ships are identified by type of ship and unique 
hull number within that type.

aDefense POW/MIA Accounting Agency— Laboratory, Offutt AFB, 
NE, USA

*Correspondence to: Carrie Brown, Defense POW/MIA Accounting 
Agency— Laboratory, 106 Peacekeeper Dr., Bldg. 301, Offutt AFB, 
NE 68113- 4006, USA 

e- mail: carrie  .a  .brown40  .civ@mail  .mil

Received 14 June 2018; Revised 13 August 2018;  
Accepted 30 August 2018

CASE REPORT

The USS Oklahoma Identification Project

Carrie Browna*

ABSTRACT: This unique case report outlines the historical and present- day analyses to identify the nearly 400 individuals who were 
casualties on the USS Oklahoma when it was hit on 7 December 1941 during the Japanese bombing of Pearl Harbor. The project is ongo-
ing, but 152 identifications based on dental, anthropological, and DNA evidence have been made as of 9 August 2018. The remains were 
buried in 62 caskets and 46 graves, and DNA and anthropological analyses have revealed them to be extensively commingled across 60 of 
the caskets. No individual identified to date has had remains originating from a single casket. The background of the assemblage, extent of 
commingling, and other challenges encountered are discussed.

KEYWORDS: forensic anthropology, commingling, USS Oklahoma Identification Project, military identification



Brown 103

FIG. 1—Aerial view of Battleship Row on December 7, 1941. The arrow indicates the position of the Oklahoma. Image available at http:  //navsource  .org 
 / archives  /01  /043  /014303a  .jpg.

FIG. 2—View of the capsized Oklahoma. Image available at http:  //navsource  .org  /archives  /01  /037  /013741o  .jpg.

http://navsource.org/archives/01/043/014303a.jpg
http://navsource.org/archives/01/043/014303a.jpg
http://navsource.org/archives/01/037/013741o.jpg


104 The USS Oklahoma Identification Project

that the remains would ultimately be identified as a group 
assemblage drove analytical decisions and processes, includ-
ing sorting the remains by element in order to bury them in 
as few caskets as possible.

When the request to bury the Oklahoma remains as a 
group was denied, analysts were tasked with reprocessing the 
remains in order to segregate the skeletal elements into indi-
viduals. Trotter (1949) reports that segregations were attempted 
based on articulation, size, color, morphology, and/or tex-
ture. These techniques were not enough to  effectively segre-
gate the commingled remains, and Dr. Trotter agreed to 
certify only the segregation of the cranial and/or mandibu-
lar remains of 27 individuals based on dental records (Harris 
2010). She would not, however, certify any other segrega-
tions, including those of postcranial remains associated to 
the 27 crania/mandibles, due to her belief that the postcranial 
associations were not made in a scientifically sound manner 
(Harris 2010). The inability to segregate the remains into 
individuals for identification was likely due to the highly 
commingled nature of the assemblage and limitations of sci-
entific techniques at the time, especially in the absence of DNA 
technology, and possibly also related to the demographic sim-
ilarities of the decedent population.

The Office of the Quartermaster General, with oversight 
of AGRS, did not approve of these 27 cranial/mandibular 
segregations, as they felt that portions of these individuals 
could still be present in the commingled assemblage. There-
fore, all disinterred Oklahoma unknowns were declared 
unidentifiable in 1949 and reburied as unknowns in 62 caskets 
within 46 graves at the National Memorial Cemetery of the 
Pacific (i.e., the Punchbowl) (Harris 2010). This left the num-
ber of unaccounted- for Oklahoma service members at 394.

Present- Day Analyses

The present- day analyses of the Oklahoma remains are 
divided into two time periods: 2003 to 2015 (pre- project) and 
2015 to present (project).

2003 to 2015

Based on research conducted by a Pearl Harbor survivor, it 
was believed that a single casket buried in the Punchbowl 
contained the remains of five Oklahoma casualties (Harris 
2010). The casualties in this casket were associated with 
Dr. Trotter’s work— specifically, segregations that she would 
not sign off on but felt that crania and/or mandibles could be 
reliably identified using dental records. The Joint POW/MIA 
Accounting Command (JPAC)— a predecessor to the present- 
day DPAA— agreed to disinter this casket in an attempt to 
identify the remains.

Ultimately, all five of the individuals who were believed 
to be in this casket were identified in the years following its 

disinterment, but a larger problem was revealed. In addition 
to the cranial remains of these five individuals, there were 
five “bundles” of remains containing postcranial elements. 
Each of these was associated with an Oklahoma “Unknown” 
number (X- number).2 Extensive DNA testing of nearly 200 
of these elements indicated that 95 distinct mitochondrial 
DNA (mtDNA) sequences were present. In other words, the 
remains in the first casket represented a minimum of 25% of 
the Oklahoma casualties.

The disinterment of the remainder of the caskets was put 
on hold until the Department of Defense and other agencies 
could agree on a course of action. This included the need to 
collect DNA reference samples from Oklahoma families and 
compile relevant antemortem medical and dental records 
from unaccounted- for service members. Collection of refer-
ence samples included maternal relatives for mtDNA com-
parisons and relevant references for nuclear comparisons, to 
include paternal relatives for Y- chromosome short tandem 
repeat (Y- STR) testing and siblings and children for autoso-
mal short tandem repeat (auSTR) testing. Self- references, 
especially for World War II cases, are extremely rare, and the 
DPAA identification process largely relies on mtDNA test-
ing, with increasing use of nuclear testing as applicable and 
available.

In 2007 a single casket that was associated with Pearl 
Harbor losses but not a specific ship was disinterred from the 
Punchbowl. No commingling was detected, and this casket 
was quickly identified as a single Oklahoma loss.

On 14 April 2015 the Deputy Secretary of Defense 
approved the disinterment of the remaining 61 caskets asso-
ciated with the Oklahoma (Work 2015). A timeline of five 
years was given to identify as many as possible of the 388 
individuals carried as unaccounted- for following the previ-
ous decade’s efforts.

2015 to Present

Following the approval to disinter, remains were exhumed 
from the remaining 45 graves at the Punchbowl starting in 
June 2015. The exhumations were complete six months later, 
in November 2015. DNA sampling began in June 2015, and 
samples were sent to AFDIL on Dover Air Force Base, Del-
aware, where analyses began immediately.

The first identifications from the large- scale Oklahoma 
disinterment were made in September 2015, based on dental 
records. By April 2016 nearly 5,000 DNA samples had been 
taken and submitted to AFDIL for mtDNA sequencing. The 
number of samples submitted in 11 months represents a record 

2. X- numbers were assigned to cases that could not be identified  
and were most commonly assigned by cemetery, forming a two- part 
numbering system (e.g., Nu’uanu X- 97). The Oklahoma X- numbers were 
assigned in ascending order based on order of recovery (i.e., a lower 
number indicates remains that were recovered earlier). However, based 
on the processing that occurred from 1947 to 1949, it is doubtful that the 
X- numbers are truly meaningful for individual elements.



Brown 105

for both the DPAA and AFDIL laboratories. One month later, 
in May 2016, the full inventory of the project was also com-
pleted (described below). During the sampling and inventory 
phase, identifications were also being made.

Analytical Procedures

Inventory

Upon accessioning, the remains in each casket were unpacked 
and cleaned by bundle at the DPAA Laboratory in Hawai’i, 
and each element was labeled with its X- number as a proxy 
for provenience. The remains were then repackaged and sent 
to the DPAA Laboratory in Nebraska, where analysts were 
assigned to conduct an inventory of the remains. Assign-
ments were made by grave, also referred to as group num-
ber, so that the same analyst was responsible for the entire 
contents of a single grave. Since there were 62 caskets bur-
ied in 46 graves, some graves have two caskets while others 
have one. Inventory progressed through the groups in ascend-
ing order and included the first group from the casket disin-
terred in 2003.

The inventory process entails examining the remains by 
bundle, identifying and siding all elements, marking com-
pleteness using zones (Knüsel & Outram 2004), collecting 
data by element, assigning each element a unique designator 
(see below), and nominating samples for DNA testing. Some 
DNA samples were collected prior to the inventory process. 
Where this was the case, the samples taken were recorded 
and assessed; if additional samples were deemed necessary, 
the analyst nominated them. Data collection included: stan-
dard and supplemental measurements3 (Byrd & Adams 2003; 
Byrd & LeGarde 2014; Moore- Jansen et al. 1994);4 epiphyseal 
fusion and pubic symphysis component scores (McKern & 
Stewart 1957); antemortem trauma, to include fractures and 
pathologies; perimortem trauma; unique or otherwise poten-
tially individuating characteristics (e.g., septal aperture); and 
taphonomic observations. These data were then entered into 
a single Excel spreadsheet.

All elements were tagged with their unique designator— 
composed of the CIL case number, group number, X- number, 
and numerical designator by region of the body— using 
small paper tags with string or by adding the information to 
the DNA sampling tag. Numerical designators were by the 
hundreds, with each set of 100 representing a different body 

3. A list of measurements and their descriptions can be found at 
https://cora  - docs  .readthedocs  .io  /en  /latest  /forensics  - anthro  - guide 
 / measurements  /. A measurement guide that standardizes the numbering 
systems across multiple methods is available at https:  //osteocoder  .com 
 / wp  - content  /uploads  /2018  /04  /Standardized_Measurements  .pdf.

4. At the time data collection started for the Oklahoma project, the 
updated data- collection procedures (Langley et al. 2016) had not yet been 
released, so all measurements were taken following the Moore- Jansen et al. 
(1994) standards for consistency throughout the duration of the project.

region (e.g., 200s are the arm; see Fig. 3). This system does 
not ascribe specific numbers to a specific bone, meaning that 
there is no empirical difference in 201 versus 299 within the 
200s region, but it does allow for easy recognition of the 
region of origin of the element (i.e., 201 is not always a right 
humerus, but indicates a bone from the arm). Numbers are 
assigned in ascending order to elements within a particular 
region as they are encountered during inventory. This system 
was found to be particularly useful in the Oklahoma project, 
where the entire project was grouped under a single acces-
sion number and bundles contained duplicated elements, but 
the particular designator numbering scheme can be easily 
changed or adapted based on project context and scope.

Selection for DNA sampling first entailed an assessment 
of pair- matches and articulations within each bundle.5 This 
strategy allowed an analyst to nominate one or both paired 
bones based on their assessment of the pair within the bun-
dle or nominate only one of several bones that articulate (e.g., 
vertebrae, pelvis). This strategy was not meant to replace 
larger scale comparisons of elements, but rather as a starting 
point for DNA sampling so that a limited sub- set of elements 
would be sampled since DNA sequencing is both time-  and 
cost- prohibitive. The exception to the sampling strategy is 
the nomination of left and right humeri and tibiae regard-
less of pair- matching in order to collect data on historical 
and present- day pair- matching accuracy (see below and 
LeGarde 2019). All portions of the inventory process were 
peer- reviewed.

Segregation

Once the elements are sampled, the samples are sent to AFDIL 
for the first round of sequencing, which targets mtDNA hyper-
variable regions 1 and 2 (HVR1, HVR2). AFDIL produces a 
large Microsoft Excel spreadsheet that compares the polymor-
phisms of each sample for both HVR1 and HVR2 to all other 
samples in the project as well as all family reference samples 
(FRS) for the Oklahoma. This spreadsheet assigns a sequence 
number to each unique group of polymorphisms seen in the 
Oklahoma data set, and under each sequence number, all 
associated samples and service members are listed (i.e., those 
skeletal elements and FRS that have the same polymorphisms 
are listed under a single sequence number).

For the Oklahoma project, segregation of remains from 
the assemblage relies first on mtDNA sequence data due to the 
heavily commingled nature of the assemblage (see below) and 
then on anthropological associations such as pair- matching 
and articulation. An analyst is assigned work by mtDNA 
sequence, with two goals: 1. determine the number of indi-
viduals represented by the skeletal elements with the given 

5. Bundles are assumed to be historical representations of individuals, 
that is, the most parsimonious associations of elements made during the 
reprocessing efforts in the late 1940s.

https://cora-docs.readthedocs.io/en/latest/forensics-anthro-guide/measurements/
https://cora-docs.readthedocs.io/en/latest/forensics-anthro-guide/measurements/
https://osteocoder.com/wp-content/uploads/2018/04/Standardized_Measurements.pdf
https://osteocoder.com/wp-content/uploads/2018/04/Standardized_Measurements.pdf


106 The USS Oklahoma Identification Project

mtDNA sequence and 2. associate non- sampled or not yet 
sequenced elements from the greater project assemblage. 
Additional nuclear DNA testing— Y- STR and auSTR— may 
be needed to aid in the segregation process, and analysts, 
along with the project lead, make recommendations to 
DPAA Laboratory management. Other regions of the mtDNA 
genome may be helpful for segregation (e.g., VR1, VR2), and 
upon AFDIL’s recommendation, elements also can be tested 
for these regions.

Nuclear testing is not generally used as a first line of seg-
regation at the DPAA Laboratory or in the Oklahoma proj-
ect because of the success in sequencing mtDNA from the 
remains encountered by the DPAA Laboratory and because 
the majority of FRS are maternal. However, nuclear testing 
is useful when attempting to segregate sequences that have 
elements from two or more individuals. In these instances, 
when an analyst is unable to fully segregate multiple indi-
viduals in a given mtDNA sequence using anthropological 

methods such as visual pair- matching, articulation, and 
osteometric sorting (Byrd 2008; Byrd & Adams 2003; Byrd & 
LeGarde 2014), additional testing is requested to attempt 
to further separate remains. The type of testing requested is 
dictated by what references are available for service mem-
bers associated via mtDNA and success rates of sequencing 
for the project as a whole. In the Oklahoma project, Y- STR 
testing is slightly more successful and there are more Y- STR 
FRS than auSTR FRS, so it is usually requested first.

Association of elements without DNA data is done by 
successfully pair- matching or articulating these elements to 
those yielding a specific mtDNA sequence. For pair- matching, 
the known element’s measurements are compared to all con-
tralateral element measurements in the entire assemblage 
using an automated version of osteometric sorting (Byrd & 
Adams 2003; Byrd & LeGarde 2014; Lynch 2018a, 2018b; 
Lynch et al. 2018; also see below). Those elements that can-
not be excluded as matching the known element based on 

FIG. 3—Homunculus depicting the regional designator numbering scheme used for inventory.



Brown 107

FIG. 4—Availability of antemortem data for Oklahoma casualties, 
expressed as percentages. A total for all DNA FRS is given (FRS All), 
and DNA is also divided by type (mtDNA, Y, autosomal).

measurements are then visually compared by the analyst, 
with potential morphological differences recorded on a dia-
gram for the known specimen prior to comparison. If a 
potential match is identified, the morphology of the match is 
recorded on a second diagram, and the known specimen and 
potential match diagrams are compared for similarities. For 
articulations, generally only those with high reliability are 
examined and included in the absence of DNA data (e.g., pel-
vis, vertebrae; see Hines et al. 2014), and only those within 
the same original bundle are assessed. Occasionally, 
mandible- to- cranium articulations are employed to associate 
elements, but these associations are made only if the DPAA 
Laboratory odontologists agree.

Once the analyst has determined the number of individ-
uals present and associated additional elements with those 
sequenced, elements are compared for size differences using 
osteometric sorting regression to ensure that all elements 
attributed to a single individual are consistent in size (Byrd & 
Adams 2003; Byrd & LeGarde 2014; Lynch 2018b). A segre-
gation is complete once all elements have been attributed to 
discrete individuals and assigned an individual number (e.g., 
I- 100). In cases where this is not possible, any remaining ele-
ments will be written up as non- attributable and remain in 
the parent sequence, rather than being assigned an individual 
number.

Segregation analysis is peer- reviewed in its entirety. Fol-
lowing peer review, a Forensic Anthropology Report (FAR) 
is written for each segregated individual. This report includes 
the biological profile, any noted antemortem or perimortem 
trauma, and any potentially individuating characteristics.

Association

The association process is the means by which a service 
member’s name is tied to a specific set of remains. For the 
Oklahoma, the results from the FAR are compared to the DNA 
results, dental records, and antemortem biological data in 
order to make a recommendation for identification to DPAA 
Laboratory management. At this point, additional nuclear test-
ing (Y- STR or auSTR) may also be requested or employed in 
order to make or strengthen the association. The final associ-
ation is only as strong as the antemortem data that are avail-
able for each service member.

The Sample

Antemortem Data

The available antemortem data for Oklahoma casualties are 
given in Figure 4. Antemortem biological data are drawn 
from military records and available for the majority of the 
Oklahoma casualties. All are adult males between the ages 
of 17 and 52 years at time of death, with a mean age of 

24.5 years and a standard deviation of 6.4 years (n = 394). The 
mean stature is 68.6 inches, with a standard deviation of 2.3 
inches (n = 376; unknown for 18 individuals). Military records 
indicate that 359 individuals are “White,” 12 individuals 
are “Black,” and 3 are “Asian (Pacific Islander)”; 20 are of 
unknown ancestry.

DNA FRS are available for 85% of the casualties, though 
the numbers are different per DNA type (see Fig. 4). The 
most common FRS type is mtDNA. Only three individuals 
have chest radiographs on file, but due to the high success 
rate of mtDNA sequencing for the Oklahoma remains— 
nearly 99% of samples sequenced for mtDNA to date have 
yielded results— this line of evidence has not yet contributed 
to an Oklahoma identification.6

Dental records are available for just under 80% of the 
casualties, but the strength of this line of evidence varies 
among the service members. For example, when only induc-
tion records are available, they are more useful for an indi-
vidual with an age at death of 18 versus someone with an age 
at death of 52, since a greater amount of time has passed 
between the dental exam and death. A greater amount of time 
between exam and death means that potentially more dental 
work could be present but not recorded, which presents chal-
lenges for associating dental remains with one service mem-
ber over another.

Postmortem Data

The Oklahoma assemblage consists of nearly 13,000 skeletal 
elements buried in 392 distinct bundles. This number includes 
both identifiable elements and unidentifiable fragments, 
although nearly 90% of the elements are both identifiable and 

6. The method of radiographic comparison using chest radiographs is 
employed by the DPAA Laboratory because of challenges in obtaining 
DNA from certain cases. This method compares a service member’s 
antemortem chest radiograph to the remains present (clavicles, lower 
cervical vertebrae, and upper thoracic vertebrae) to make an 
identification (Stephan et al. 2011).



108 The USS Oklahoma Identification Project

complete. Fragmentation of the elements is minimal, and 
preservation is excellent.

Of the 62 caskets, 60 contained two or more bundles. For 
these 60 caskets and 390 bundles, on average, there were 8.9 
bundles per casket and 32.1 elements per bundle, with a min-
imum of 4 and a maximum of 175 elements per bundle. These 
numbers do not include teeth or unidentified fragments.

The MNI represented by the assemblage using the most 
numerous duplicated element (cranium) is 357, though the 
thorax (700; ribs and sternum) has the highest total number 
of elements recovered (Fig. 5). When combining mtDNA 
sequences and skeletal duplication (i.e., the most numerous 
element for a particular sequence gives the MNI for that 
sequence; all individual MNI tabulations by sequence are 
then totaled across the assemblage), the MNI increases to 
400. See Palmiotto et al. (2019) for a more detailed discussion 
of estimating the number of individuals in this assemblage.

Elements are not represented equally. Figures 5 and 6 
provide data on differences in recovery rate for elements by 
region; Table 1 lists what elements are considered in these 
counts. The expected number of elements is calculated by 
multiplying the number of unaccounted- for individuals (394) 
by the number of elements in a particular series (e.g., 200 

FIG. 5—Count of elements by region, comparing observed and expected.

FIG. 6—Ratio of elements observed to expected, by region.

TABLE 1—Elements Used for the Comparison of Observed  
versus Expected Elements in the Oklahoma Assemblage.

Region Elements

100 Cranium, mandible
200 Humerus, radius, ulna
300 Carpals, metacarpals, manual phalanges
400 Femur, patella, tibia, fibula
500 Tarsals, metatarsals, pedal phalanges
600 Clavicle, scapula
700 Ribs, sternum
800 Vertebrae
900 Innominate, sacrum, coccyx

[arm] = 6). While this does not take into account potential 
pairs or refits of fragmented elements, this calculation pro-
vides an easy comparison in terms of assemblage composi-
tion. It is important to note that observed totals do not 
approach expected totals even for the most numerous region 
(thorax), indicating that the number of elements recovered is 
always much less than what would be expected (see Fig. 5). 
Note that recovery rates for the hands (300) and feet (500) 
are especially low, while the recovery rate for the head (100) 
is the highest, followed by the arms (200) and legs (400).

When examining the remains in terms of potential pro-
venience information (i.e., X- number), there is a difference in 
terms of what X- numbers were originally buried in Nu’uanu 
versus Halawa prior to the 1947– 1949 processing (Fig. 7). 
All X- numbers less than 100 were originally buried in 
Nu’uanu cemetery, while those greater than 100 were buried in 
Halawa. It might then be expected that individuals recovered 
first and buried in Nu’uanu would be less commingled than 
those recovered later and buried in Halawa. Yet, the results 

FIG. 7—Relationship of X- number (bundle) to original cemetery.



Brown 109

FIG. 8—Relationship of X- number (bundle) to the number of elements 
in the bundle representing it.

seen thus far suggest that the commingling that occurred 
during the reprocessing efforts does not seem to have occurred 
within only one cemetery group (i.e., elements from X- numbers 
less than and greater than 100 are commingled together).

Given the extensive commingling noted in this assem-
blage, it is interesting that there is still a negative correlation 
between the X- number and the number of elements in the 
bundle representing it (Fig. 8); a higher X- number is associ-
ated with fewer elements. This makes sense in terms of 
recovery efforts in the 1940s, since X- numbers were assigned 
in ascending order, and those remains recovered earlier are 
likely to have more elements than those recovered months 
and years post- incident. However, given the reprocessing 
that occurred from 1947 to 1949 it is unclear why the rela-
tionship still holds true today, since presumably all elements 
were equally commingled during the reprocessing phase in 
the 1940s, especially given what is known about the extreme 
commingling across the entire assemblage (see below). It is 
possible that X- numbers were reassigned during the repro-
cessing phase, so that those remains that were more com-
plete were given lower X- numbers. If this is the case, the 
X- numbers are virtually meaningless in terms of aiding in 
present- day segregations given what is known about how 
great the commingling is.

Extent of Commingling

Based on the mtDNA results from the first casket, where 25% 
of the Oklahoma casualties are represented by at least one 
skeletal element, it was expected that commingling was 

extreme. Disinterment of the remainder of the caskets con-
firms this. With the exception of two caskets, multiple bun-
dles are present in each casket, and none of these bundles 
contain elements from a single individual. Conversely, no 
individual identified to date has skeletal elements from only 
a single bundle or even a single casket.

A preliminary investigation of historical element asso-
ciations within bundles confirms Dr. Trotter’s fears that seg-
regations were being made arbitrarily, at least in part (Brown 
et al. 2017). Using mtDNA results, Brown et al. (2017) found 
that the humeri and tibia are correctly associated to their 
antimeres 44% and 46% of the time, respectively, but only 
6% of the time when humeri are compared to tibiae in the 
same bundle. While the pair- matching numbers may seem 
low, it is important to remember that the comparisons under-
taken were on the order of 100,000 given the presence of 
approximately 300 elements of each side for both the humeri 
and tibiae. Thus an accuracy of 50% may represent the best- 
case scenario historically given the limitations of methods 
70 years ago. However, 6% likely represents nothing more 
than chance.

Figures 9 and 10 demonstrate the extent of commin-
gling; Figure 9 depicts a single bundle, and Figure 10 depicts 
an identified individual. In Figure 9, the initial by- element 
inventory on the left does not indicate commingling when 
just element duplication is considered. However, when mtDNA 
sequences are overlaid, 12 different sequences are seen. Thus, 
a bundle that appears on first glance to be a single individual 
actually represents portions of at least 12 individuals, and 
likely more given that not all elements are sampled and the 
rarity of the mtDNA sequence is not considered here.7

In Figure 10, that of an identified individual, all skeletal 
elements are from the same mtDNA sequence, but this time 
the origin of the elements by bundle (X- number) is depicted. 
For this individual, who has 17 elements present, 15 came 
from different bundles. Notably, the cranium/mandible and 
innominate/femur have different sequences, which may speak 
to the lack of reliability of these articulations for associa-
tion. Both the historical tibia pair- match and the radius- ulna 
articulation were correct in isolation but were not correct in 
terms of association to a single individual.

While not all DNA samples have been sequenced, thus 
far the data indicate that, on average, commingling is around 
80% per bundle. That means that for every 10 elements 
sequenced in a bundle, 8 will return a different mtDNA 
sequence. Thus using a bundle as a true provenience is not 
possible, and there appears to be no true relationship among 
elements in any given bundle.

7. Rarity of the sequence is determined by AFDIL and is given as  
the number of times a group of polymorphisms is seen in the AFDIL 
population database (n = 10,428). For the Oklahoma project, rarity ranges 
from 0 to 360 out of 10,428.



110 The USS Oklahoma Identification Project

FIG. 9—Homunculi depicting a single bundle of remains. Left, initial by- element inventory with no skeletal duplication; right, elements sampled with 
sequences indicated. The homunculus on the right does not include elements articulated or pair- matched. Note: multiple ribs are present, but only the 
one sampled is depicted; the teeth are not depicted.

FIG. 10—Homunculi depicting an identified individual. Left, all elements present in a single mtDNA sequence with a single match to an Oklahoma FRS; 
right, element provenience (X- number) indicated. Note: the teeth are not depicted.



Brown 111

FIG. 11—Oklahoma identifications by fiscal year (FY). The DPAA FY 
runs from 1 October to 30 September. Note the uptick in identifications 
following the exhumations in 2015 and the increasing pace of identifica-
tions in 2018 due to receipt of increased numbers of mtDNA results. 
Data as of 9 August 2018.

Identifications

Oklahoma identifications are made using a combination of 
DNA, dental, and anthropological analyses. As of 9 August 
2018, 152 identifications had been made (Fig. 11). This means 
that three years following the disinterment of the majority of 
Oklahoma caskets, 35% of the individuals who were unac-
counted for following World War II have been identified.

Identifications have been made in three phases: pre- 
project (2003 to 2010), initial project (September 2015 to 
April 2017), and project (July 2017 to present) (see Fig. 11). 
The identifications made prior to the project were those from 
the initial 2003 Oklahoma casket and the single 2007 Pearl 
Harbor– associated casket. The five identifications from the 
2003 disinterment were cranial/mandibular only, and there-
fore it is expected that there will be postcranial portions of 
these individuals commingled with remains from other cas-
kets. The 2007 identification represents a complete set of 
remains, so it is not expected that commingling of this indi-
vidual will be seen in the larger Oklahoma assemblage. The 
initial project identifications relied largely on dental identifi-
cations, with some support from DNA. During this phase, 
only crania and/or mandibles were identified. Like five of the 
individuals from the pre- project identifications, it is expected 
that additional remains will be associated with these individ-
uals as the project progresses.

Project identifications include cranial and postcranial 
remains. These cases are worked fully by the Oklahoma team 
and are presented to DPAA Laboratory management, includ-
ing the DPAA Medical Examiner (ME), and AFDIL on a 
regular basis. Once DPAA Laboratory management and the 
ME agree on the association proposed by the team, the case 
moves forward for identification. Identifications are made by 
the DPAA ME, and families are notified by the respective 
Service Casualty Office. For the Oklahoma this is the Navy 
and the Marine Corps.

Challenges

Beyond the extensive commingling, additional challenges 
were encountered during the inventory and analysis of the 
Oklahoma assemblage. Due to the size of the assemblage, 
data management and analysis became increasingly difficult 
in terms of data integrity, access, and scale of comparisons 
as inventory and analysis progressed.

The project was initially inventoried on paper forms and 
then data were entered into a Microsoft Excel spreadsheet. 
This worked relatively well when only one person was work-
ing on data entry, but as the project team grew it became very 
difficult to continue, since Excel only allows one individual 
access at a time. Attempts to work in different spreadsheets 
and merge them together were not successful, and data were 
often inadvertently deleted, moved, or altered. Using Mic-
rosoft Access did not fix these issues, and a more sophisti-
cated option was envisioned.

The Commingled Remains Analytics (CoRA) multi- user 
web application was developed in a partnership with the Uni-
versity of Nebraska at Omaha’s College of Information Sci-
ence and Technology. This application enables by- element 
inventory; biological profile, trauma, and taphonomy data 
collection; assignment and DNA tracking; and overall project 
management for commingled remains. The hope for future 
development of CoRA includes the ability to integrate other 
anthropology applications (e.g., FORDISC, OsteoSort). Cur-
rently, CoRA is only available for internal use by DPAA, but 
it is anticipated that it will be released in the future for pub-
lic use. Additional information about CoRA can be found at 
https:  //cora  - docs  .readthedocs  .io  /en  /latest  /.

Comparisons of elements across the Oklahoma assem-
blage also presented a challenge. With major long bones num-
bering around 300 for each side, pairwise comparisons for a 
single element were over 100,000 and precluded by space and 
time. In order to harness the power of osteometric sorting, 
OsteoSort was developed to automate the association process 
(Lynch 2018a, 2018b; Lynch et al. 2018). OsteoSort is avail-
able online at https:  //osteocoder  .com  /, and online applica-
tions include single pairwise comparisons, articulations, and 
regression analyses as well as antemortem stature compari-
sons to maximum length measurements. If multiple element 
comparisons are desired, OsteoSort can also be run in the 
statistical package R (R Core Team 2014). More information 
about OsteoSort is available on the above- cited website.

Conclusion

The Oklahoma assemblage provides unique opportunities 
to better our understanding of techniques used to resolve 
commingling, as well as insight into historical forensic 
anthropological investigations. Because the elements are 
largely complete and well preserved, the assemblage offers 

https://cora-docs.readthedocs.io/en/latest/
https://osteocoder.com/


112 The USS Oklahoma Identification Project

an excellent opportunity to research current methods and 
develop new ways of analyzing commingled remains. It is 
anticipated that in addition to the research in this issue, further 
research on recovery rate, MNI, age estimation, osteometric 
sorting, and reliability of articulations will be conducted, espe-
cially once DNA sequencing is complete.

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