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Bone Histology Sampling Sites for the Identification of Undocumented Border Crosssers along the U.S.-Mexico Border



After attending this presentation, attendees will understand the difficulties of estimating age-at-death of Undocumented Border Crossers (UBCs) along the U.S.-Mexico border, and the importance of sampling site choice for histological age estimation. This presentation will impact the forensic community by helping to resolve the issues anthropologists face working to identify UBCs in the growing humanitarian crisis afflicting the U.S.-Mexico border.
Lauren A. Meckel, BS1*; Sophia R. Mavroudas, MA1; Victoria M. Dominguez, MA2; M. Katherine Spradley, PhD1
1Forensic Anthropology Center at Texas State University, Department of Anthropology, San Marcos, TX 78666; 2Skeletal Biology Research Laboratory, Division of Anatomy, The Ohio State University, Columbus, OH 43210
Bone Histology Sampling Sites for the Identification of Undocumented Border Crossers
along the U.S.-Mexico Border
The death of Undocumented Border Crossers (UBCs)
along the U.S.-Mexico border is a largely ignored
humanitarian crisis in the United States.
As a collaborative effort the Forensic Anthropology Center
at Texas State (FACTS), The University of Indianapolis,
and Baylor University have been working to identify UBCs
from Brooks and surrounding counties in Texas. As part of
this effort, FACTS has accepted 78 UBCs from
exhumations and from the Webb County (Texas) Medical
Examiner’s Office.
A critical aspect of UBC identification is an accurate age-
at-death estimate to narrow the list of potential matches for
repatriation. However, the immense skeletal diversity
represented within this group present new challenges in
identification as population specific methods are lacking
for these individuals.
Previous studies have confirmed that combining both
gross morphology and histomorphology age estimation
techniques provides a more complete picture of age
related skeletal changes1.
The Skeletal Biology Research Laboratory at The Ohio
State University for the assistance in methods and rib
The anthropology faculty and students at the University
of Indianapolis, Baylor University, and Harris Co. for
assistance, their field work, and research for the
purposes of migrant identification.
Nicole Crowe, Annie Riegert, and Devora Gleiber for
their assistance in slide preparation.
Broader Impact
Efforts for identification should incorporate histological
methods in the recovery protocol for a more efficient
identification process.
Identification of the limitations of histological age
estimation in UBCs is critical when the recovery of
skeletal elements is limited to long bones.
Further investigation into the histomorphological age of
border crossers outside of Texas may give clues to
differences between groups which could subsequently
assist in regional identification.
Inter-observer error between 3 observers was not significant (p > .05)
1. Mavroudas S, Spradley MK, Fancher JP, Duecker H,
Crowe C. 2015. The identification of undocumented border
crossers along the U.S.-Mexico border: A case for bone
histology. 2015 Proceedings of the American Academy of
Forensic Sciences Meeting 21:71.
2. Stout SD, Paine RR. 1992. “Brief communication:
histological age estimation using rib and clavicle.” Am J
Phys Anthropol 87(1): 111-115.
3. Cho H, Stout SD, Madsen RW, Streeter MA. 2002.
“Population-specific histological age-estimating
method: a model for known African-American and
European-American skeletal remains.” J Forensic Sci
47(1): 12-18.
4. Thompson DD. 1979. “The Core Technique in the
Determination of Age at Death in Skeletons.” J Forensic
Sci 24(4): 902-915.
The results of this study indicate that the mid-shaft of the
6th rib is the most appropriate histological sampling site
for UBC identification.
Overall, the femur method was a poor indicator of UBC
skeletal age.
Future research focusing on the anterior femur of UBC
groups could prove appropriate for UBC identification if
new methods are developed with appropriate age
Method Accuracy Inaccuracy Bias
Femur 21% 20.1 10.4
Rib 88% 7.1 3.2
*Accuracy is determined as a percent of point estimates that fell into the gross morphology range. Inaccuracy is
the average distance in years from the gross morphology median and bias is a measure of how many years the
sample was under/over aged.
FIGURE 1: Histological cross-section of a rib (a) showing osteons counted
for age estimation (b).
Figure 2. Point age estimates for each individual across all three methods
Identified Case Example
This individual was found in Hidalgo Co. Texas in 2013. Once his remains
arrived at Texas State, a full skeletal analysis was completed including
sampling for histology and DNA. DNA collected at the Missing Persons Day in
Harris County 2015 event was a match. He was identified as a 53 year old
Hispanic Male from Mexico.
years 46-70
years 22-40
Actual Age
Gross Age Rib Age Femur Age
The aim of this study is to determine which bone histology
sampling site is the most appropriate indicator of UBC age-
at-death. This will help increase identifications by
narrowing down missing persons lists and gaining a better
understanding of skeletal age in UBCs.
N= 24 individuals, 11 males and 13 females.
Samples were taken from the mid-shaft of the left 6th
rib and the anterior mid-shaft of the left femur
(Figure 1).
Histological point age estimates based
independently on the rib2,3 and the femur4 were
compared to estimated gross morphology age
ranges for each individual (Figure 2).
Gross age ranges were obtained using standard
gross morphology skeletal age indicators and
information gathered from published case reports.
a. b.
Table1. Accuracy, inaccuracy, and bias were calculated for each
histology method and compared to median gross age.*
Materials and Methods
Femur Rib Gross Morphology
Mean Age
Mean Age
Figure 3. Mean age estimates for each method
12345678910 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Femur Age
Rib Age
Gross Age
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Full-text available
Histological methods for estimating age at death using osteon population densities for the rib, clavicle, and rib and clavicle combined are presented. Predicting formulas were generated from a sample of 40 individuals of known age, sex, and race. Independent samples of 12 ribs and 7 clavicles were used to test the formulas. Mean differences between known and predicted ages were 1.1 years, 2.6 years, and 3.4 years for the clavicle, rib and clavicle combined, and rib formulas respectively. An analysis of variance found no significant differences among the means for predicted and known ages. Since the formula based upon rib and clavicle combined has the higher standard error and r2, and includes data from different bones, it should provide better overall accuracy and reliability, and is recommended whenever both bones are available.
This study proposed an histological method of estimating age at death in skeletons that uses a 0.4-cm-diameter core of cortical bone. Age-estimating regression equations were generated from data obtained from the analysis of bone cores taken from femurs, tibiae, humeri, and ulnas of cadavers. When the regression equations generated in this study were applied to eight forensic science cases, accurate ages at death were estimated.
Previously developed histological age-estimating methods have been based on samples lacking interpopulation variability. A comparison of age-associated rib histomorphometrics between an European-American sample and an African-American sample indicates that ethnicity can have a significant effect on osteon population density (OPD), osteon cross-sectional area (On.Ar), and relative cortical area (Ct.Ar/Tt.Ar). Based upon these findings, new histological age-predicting formulae are presented that are recommended when estimating age for African-American or European-American skeletal remains. A general formula that is applicable to remains of unknown ethnicity is also provided.
The identification of undocumented border crossers along the U.S.-Mexico border: A case for bone histology
  • S Mavroudas
  • M K Spradley
  • J P Fancher
  • H Duecker
  • C Crowe
Mavroudas S, Spradley MK, Fancher JP, Duecker H, Crowe C. 2015. The identification of undocumented border crossers along the U.S.-Mexico border: A case for bone histology. 2015 Proceedings of the American Academy of Forensic Sciences Meeting 21:71.