Skeletal Sex Estimation and Practitioner Use of MorphoPASSE

Skeletal Sex Estimation and Practitioner Use of MorphoPASSE

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This webinar originally occurred on October 5, 2022
Duration: 1.5 hours


Skeletal sex estimation is one of the most important aspects of the biological profile as it narrows the population essentially by half and aids in decedent identification. This presentation briefly discusses the current state of skeletal sex estimation in forensic anthropology. Topics covered in this overview section include appropriate terminology, practitioner preferences, morphological and metric methods, statistical approaches, current standards/best practice guidelines, challenges and contentious issues, and future directions and research needs. The primary focus of the presentation moves on to the MorphoPASSE: Morphological Pelvis and Skull Sex Estimation database and program for skeletal sex estimation.1 The presentation details the revised trait descriptions and scoring procedures, with examples, and demonstrates how to use the MorphoPASSE graphical user interface (GUI) and interpret the output. By the end of this presentation, practitioners will be comfortable applying the MorphoPASSE method to skeletal sex estimation in forensic contexts. 

MorphoPASSE is a free GUI designed to combine the five skull traits of Walker (2008)2 – glabella, nuchal crest, supraorbital margin, mastoid process, mental eminence – with the three pelvic traits of the Klales et al. (2012)3 method – ventral arc, subpubic contour, medial aspect of the ischiopubic ramus – into a single estimate of sex using a machine learning method known as random forest modeling. Prior to creation of the MorphoPASSE GUI, the validity of the original Walker and Klales et al. methods were tested. Intraobserver and interobserver reliability in trait scoring was assessed, trait descriptions/images were revised, secular change and population variation were evaluated, and the impact of asymmetry was analyzed through grant funding. The resulting program and combined method, the MorphoPASSE GUI, contains a sample of over 2,500 individuals with known demographic data from 15 worldwide collections.

Traits are to be scored using the MorphoPASSE manual4 which includes the revised trait descriptions, illustrations, and real-bone figures. These scores are then put into the MorphoPASSE GUI. A detailed overview of each trait, along with individual ordinal trait scores and associated descriptions and images, are covered. Challenging specimens, unique cases, and real case specimens are also included as examples. Once the available traits are scored and entered into the MorphoPASSE GUI, practitioners can select the appropriate comparative sample for their unknown case based on temporal period, ancestry/population group, and/or worldwide region. This presentation details the recommended parameters for active forensic casework and present several case examples.

Finally, practitioners are presented with the results output, which includes case predictive probability for sex membership, sample size and parameters, test accuracy, training model accuracy, and model variable importance. Using case examples, the output is described in detail and a sample results section write-up for a forensic anthropology case report is presented. 

Detailed Learning Objectives

  1. Attendees will understand the current state of skeletal sex estimation in forensic anthropology.
  2. Attendees will learn how to collect, analyze, and interpret data for use in MorphoPASSE.
  3. Attendees will be able to apply the MorphoPASSE program to cases for skeletal sex estimation.


  • Alexandra Klales, Ph.D., D-ABFA | Associate Professor of Forensic Anthropology, Washburn University

Related Resources

  1. Klales AR. 2018. MorphoPASSE: the Morphological Pelvis and Skull Sex Estimation Database. Version 1.0. Topeka, KS: Washburn, University.
  2. Walker, P.L. (2008), Sexing skulls using discriminant function analysis of visually assessed traits. American Journal of Physical Anthropology, 136: 39-50.
  3. Klales, A.R., Ousley, S.D. and Vollner, J.M. (2012), A revised method of sexing the human innominate using Phenice's nonmetric traits and statistical methods. American Journal of Physical Anthropology, 149: 104-114.
  4. Klales AR, Cole SJ. 2018. MorphoPASSE: the Morphological Pelvis and Skull Sex Estimation Database Manual. Version 1.0. Topeka, KS: Washburn, University.

Funding for this Forensic Technology Center of Excellence webinar has been provided by the National Institute of Justice, Office of Justice Programs, U.S. Department of Justice.

The opinions, findings, and conclusions or recommendations expressed in this webinar are those of the presenter(s) and do not necessarily reflect those of the U.S. Department of Justice.

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