Unit 2 Forensics

Biological Profile

Not an ID, describes characteristics of unknown individuals, provides estimates, can be developed when ID is unknown, sex estimation, population affinity, age estimation, stature estimation

Sex estimation

Phenice/Klales pelvis, Walker skull, post cranial, MorphoPASSE, FORDISC

Population affinity

Skull (m/nm), post cranial (m/nm), FoRDent, MaMD, Hefner macromorphoscopic, (hu)MANid

Age Estimation

Growth and development juvenile, maturation and degeneration adults, pelvis, rib ends, cranial sutures, clavicle, London Atlas for juvenile teeth, long bone dimensions/epiphyseal unions for juvenile, pelvis Suchy Brooks/Hartnett/Osborne, TA2/TA3, ADBOU

Stature Estimation

Long bones, vertebrae, linear regression method (pop/sex specific), anatomical method (fully, requires mostly complete remains, more accurate than linear regression)

Biomechanics

influence robusticity of muscle attachment sites

Secular change

Changes in environment, socioeconomic status, nutrition cause populations to change over time

Sources of uncertainty

Biological variation, reference sample differences, condition of remains, method specific limitations, observer error, practitioner differences, different methods may produce different estimates

Osteometrics

Bone measurements, used to compare groups, geometric morphometrics (3skull, digitizer)

Craniometrics

Helps analyze quantitative variation in morphology, two dimensional 34 measurements, three dimensional osteoware craniometrics and 3skull 60 measurements based on Howells 34 FD measurements

Type 1 landmark

Defined by the juxtaposition of different tissue

Type 2 landmark

points of maximum curvature, have to use calipers

Type 3 landmark

extreme points of various locations

Measurement issues

Accuracy (difference between result and true value), reliability (repeated measurements the same), precision (measurement repeatable), failure to follow instructions, misidentification of landmarks, printing errors, insufficient practice, improper tool use, variation of one observer experience (intra-observer), variation between two or more observers (inter-observer)

Sexual dimorphism

Phenotypic differences between males and females of the same species, in humans secondary sex characteristics, males are larger with longer bones and thicker muscle attachment

Sex Estimation traits Non metric

Os coxae shorter and wider for females, ventral arc, subpubic concavity, ischiopubic ramus, nuchal crest, mastoid process, supraorbital margin, supraorbital ridge, mental eminence

Cross validation

How well the would the model classify individuals whose group is already known, what percent of individuals were properly classified with the model

Mahalanobis Distance

How far is the unknown from the reference group, how many standard deviations away a data point is from the center of a multivariate distribution, smaller distance = more similar

Posterior Probability

Probability of membership in each group based on the relative distances to each group

Typicality probability

Probability that the classified individual belongs to each group based on distance, F, Chi square, ranked

Nonmetric Population Affinity traits

Rhine, Hefner: anterior nasal spine, inferior nasal spine, interorbital breadth, malar tubercle, nasal aperture width, nasal bone contour, nasal overgrowth, postbregmatic depression, posterior zygomatic tubercle, zygomaticomaxillary suture

Metric Population Affinity

Howells 57 measurements, now 37 measurements

Dental Morphology for Pop Affin

uses nonmetric tooth crown and root variations, Edgar 29 traits but not mix and match, rASUDAS 21 traits but based on archaeological samples, dental jargon and small size of teeth make it hard, shovel shape incisor, incisor diastema, tuberculume dentale, canine mesial ridge, premolar accessory cusp, metacone and hypocone, FoRDent

Weathering

Physiological process that encompasses the physical and mental effects of living in marginalized communities

Embodiment

Process by which social experience are expressed through biology

Bias in Age estimation

Age mimicry (estimated ages mimic structure of reference sample), attraction to middle, secular change

Subadult age estimation

Based on growth and development, mineralization, change in size and shape, dental formation highly structured, long bone dimensions from fetal to 10, sex and population specific, fusion (union of ossification center to diaphysis)

Adult age estimation

Based on degenerative changes, more environmental factors make it less precice, Pubic symphasis Todd/Brooks and Suchey/Harnett, sympheseal/dorsal/ventral face, Auricular surface Lovejoy/Buckberry/Osborne, sternal rib ends Ischan/Harnett, Cranial sutures, osteoarthritis, eburnation, osteoporosis, ADBOU/TA2

Requirements for useful method Age estimation

Progressive unidirectional change with age, standardized method, correlated with age, feature changes happen at the same time in all individuals of a certain group

Potential errors stature

growth, diurnal changes, human variation, sex differences, population variation, problems with reference samples

Anatomical method

articulating or measuring all the bones that contribute to height, Fully method European male sample, Raxter new correction factor measurement clarification and effects of population and sex, not sex or population specific, good for unique proportions, need nearly complete skeleton, time consuming

Mathmatical method

More commonly used, linear regression, standard error of estimate (measure of how well the regression formula fits the data), confidence interval provides the average stature for people with a certain bone length (population based), prediction interval provides likely stature of individual (individual based), FORDISC, problems due to measurements used and reference samples, must use sex and population specific formulae, do not need complete skeleton

Forensic Case Report

Formal record of an examination that explains what was recieved, what was done, what was observed, and what can be concluded, needs to be objective, accurate, includes everything, able to be defended, common pitfalls are using subjective language, presenting an assumption as an observation, using technical terms without explination, leaving out methods/results/limitations, making conclusions the evidence does not directly support, using vauge qualifiers

Structure of Case Report

Case info, background and evidence, methods, findings, interpretation and conclusions, limitations and attachments

Fixation index

genetic diversity index