Midterm 2 Flashcards
Equipment in a forensic lab
- tables and benches
- sink with hot and cold water
- fume hood
- measuring equipment
- drying racks
- reference casts
What size of table?
2x1 meters -> length of a skeleton
What measuring equipment is used?
calibers and osteometric boards
Methodological and safety issues in the lab
- Security: maintain chain of custody (restricted access, alarms, log ppl coming in and out, keep all remains separate.
- Separation of evidence units: keep skeletons separate (only have one out at a time!)
- work environment: fume hood for chemicals, stay up to date on vaccines, clean everything carefully (1% bleach solution), wear protective clothing
Preparation of remains (steps)
- examination for soft tissue trauma
- bulk soft tissue removal
- disarticulation
- residual soft tissue removal
- stabilizing remains
examination for soft tissue trauma
look for trauma to flesh
Bulk soft tissue removal
Fully clean off the soft tissue, using a scalpel and tissue scissors
-> remove muscles of torso, then limbs
-> cut tendons and peel away
Alternative method for bulk tissue removal
Dermestid beetle larvae
- takes 2-3 weeks for the beetles to eat the flesh
- smells, have to take care of the beetles
- keep some beetles afterwards for sampling
Disarticulation
- separate joints and their articulated bones (skull from spine, arms from torso, pelvis from spine, legs from pelvis)
- after those major removals separate the elbow and leg joint
Residual soft tissue removal
- soak bones in water to soften tissue, then simmer them in water and detergent for a couple of days
- degrease with benzol afterward, which takes a couple of days
- finally, bleach with hydrogen peroxide/potassium hydroxide for about a day
Alternative way of residual soft tissue removal
An antiformalin solution, which has stronger chemicals. It takes less time but can cause the bones to disintegrate
Stabilizing remains
- preserve bones in Alvar or PVA (coating)
- not used anymore because it alters the composition of bones
Reconstruction
- use a reversible adhesive, just in case you make a mistake
- don’t add stand-ins for bones!
Sorting Commingled remains
Commingled remains: bones of many individuals mixed up
- determine MNI
- group bones by type, categorize them
- determine the number of people based on the number of bones
Reassembly
- lay bones out in anatomical position and double check for:
duplication, consistency in size, if joints fit together (joint surface concurrence
Inventory
cross check with the field inventory, and mark all bones with a case number
Visual skeletal inventory & numerical inventory
Visual: pre-existing skeleton drawing (one for adults, adolescents, and children) where you color in the bones that are present
Numerical: mark fragments, number of fragments, and lefts and rights. Mark % of bone present and % of skeleton present, along with how well the the exterior is preserved.
What is sex?
biological sex -> male or female, along with categories for indeterminable and possibles
Sexual dimorphism
differences in size and shape between the two biological sexes
What is the accuracy in determining sex for the following portions of the skeleton?
1. Whole skeleton
2. Just pelvis
3. Just skull
4. Just long bones
- 90-100%
- 90-95%
- 80-90%
- 80%
What’s the difference between a male and female pelvis?
Male: large and robust
Female: small and gracile
What’s the difference between a male and female ilium?
Male: high and vertical
Female: low and flat
What’s the difference between a male and female subpubic angle?
Male: v-shaped
Female: U-shaped
What’s the difference between a male and female pubic shape?
Male: narrow and rectangular
Female: broad and square
What’s the difference between a male and female pelvic inlet?
Male: heart-shaped
Female: circular/elliptical
What’s the difference between a male and female obturator foramen?
Male: large and ovoid
Female: small and triangular
What’s the difference between a male and female greater sciatic notch?
Male: narrow
Female: wide
What’s the difference between a male and female prearicular sulcus?
Male: rare
Female: well-developed
What’s the difference between a male and female sacrum?
Male: sacrum protrudes, and is long and narrow
Female: sacrum is tucked away, and is short and broad
What are the phenice traits?
These are the golden traits for estimating sex, with an accuracy of 95%. They include:
1. Ventral Arc
2. Subpubic concavity
3. ischiopubic ramus ridge
What’s the difference between a male and female ventral arc?
Male: slight/absent
Female: strong
What’s the difference between a male and female subpubic concavity?
Male: convex
Female: concave
What’s the difference between a male and female ischiopubic ramus ridge?
Male: broad and flat
Female: narrow, crest-like
Washburn’s ischium-pubic index
(pubic length/ischium length) x 100
<84 = male, 94+ = female
68% accuracy for unknown ancestry, 83-91% if ancestry is known
What’s the difference between a male and female skull?
Male: large and rugged
Female: small and smooth
What’s the difference between a male and female chin?
Male: broad
Female: pointed
What’s the difference between a male and female mastoid process?
Male: large, projecting
Female: small, non-projecting
What’s the difference between a male and female brow ridge?
Male: large
Female: small to none
What’s the difference between a male and female frontal?
Male: slanted
Female: high, rounded
What’s the difference between a male and female suborpital margin?
Male: rounded
Female: sharp
What’s the difference between a male and female nuchal area?
Male: rugged, hooked
Female: smooth, hookless
How would you determine sex based on the traits from the skull?
- score the traits 1-5, female - male
- put into corresponding discriminant function
y > 0 = female
y < 0 = male