Module 4.2 Preparing Remains in the Lab

Where is data collection performed? What do they analyze?

• in a lab → wet lab or autopsy suite

• observation and measurement of the outer surface of the skin

How do remains arrive to the lab?

• sometimes bone surface is clean and dry

• sometimes the skeleton has adhering material

  • soft tissue in various stages of decomposition, mummification, saponification

  • clothing, jewler

  • debris from the deposition site

What do you do before processing?

• photographs and notes on the condition of the remains they arrived in

  • maybe x-rays too

• DNA samples are collected

• perform initial assessment in case evidence is lost during processing

  • trauma analysis for early evidence of healing or differential staining

  • soft tissue evidence of tattoos are scarring

Explain mechanical removal of soft tissue

• if there is a lot of tissue, remove it mechanically with scapels

• don’t remove all soft tissue with sharp edges since there is a risk of damaging or marking the bones which can impact future analysis

• disarticulate the skeleton into individual bones

Explain maceration in processing

• softening the tissues by soaking the bones in water with bacteria decomposition

• methods can vary in temperature, soak time, enzyme detergents, and level of ammonia

  • warm water is faster on adults

  • cold water used on children to prevent denaturing of cartilage

  • temperature is below boiling to avoid damage

• performed in big pots

• bones are monitored daily to prevent damage or over-processing

• maceration is done multiple times to remove all the soft tissue

Explain the use of carrion beetles in processing

• consume remaining soft tissue at any stage of decay with no damage to the bones

• processing time depends on the amount of soft tissue, condition of the remains, and the size of the colony

• creating and maintaining a colony is time consuming and needs constant feeding between forensic use

Explain the use of chemicals in processing

• bleach, antiformin, sodium hypochlorite, papain

positives:

• quick removal of soft tissue

• useful to preserve bone

• degrease dry bone that have been kept in storage for long time

negatives:

• degrades bone

• hazardous

• expensive

• specialized handling and storage

• reduces DNA yield

How do you maintain hygiene when handling remains?

• soft tissue is disposed as biohazardous waste

• tools and regular waste are autoclaved before disposal

What are some steps that need to be taken before analyzing the bones?

• after remains are processed, you should have clean and dry bones

• remains must be reconstructed (esp. if there is damage to the skeleton)

• sort through co-mingled remains if there are multiple individuals

Explain re-assembling the skeleton

• reassemble will help estimate, identify, and examine patterns of trauma

• make sure each are in the correct position and correct side

• if the remains are fractured, the skeleton must be reassembled to original anatomical locations

How do you reassemble the bones?

• use temporary reconstruction

  • tape, putty, wax, wire braces

• if using adhesives, they should be water or acetone soluble

Explain commingled remains

• when more than one individual is present and/or intermixing of skeletal elements from more than one individual

• mass graves, fatalities

• you want to identify how many people are present and separate them into individuals

How do you resolve commingling?

• document location of remains on site

• create inventory and label specimen

• sort element by type and side

  • sorting helps determine minimum number of individuals (MNI) or most likely number of individuals (MLNI)

Explain how to calculate minimum number of individuals (MNI)

• sort the elements by size and take the highest number

left: 3 humeri, 3 femur, 1 fibula

right: 4 humeri, 1 tibia

highest number = 4

there are 4 individuals

Explain how to calculate most likely number of individuals (MLNI)

• used when not all individuals are not recovered

• MLNI = [(L+1) (R+1) / (P+1)] - 1

• pick one element

pair: 1 humeri

left: 3 humeri, 3 femur, 1 fibula

right: 4 humeri, 1 tibia

MLNI = [(3+1) (4+1) / (1+1)] - 1 = 5

there are 5 individuals

What are the methods to identify individuals?

old bear play at the dance expo

1. pair matching

   • matching lefts and rights by size and shape

2. articulation

   • consistency of joints fitting together

3. osteometric sorting

   • bones of the same size are probably from the same person

4. taphonomy

   • preservation of bones like colour and condition

5. DNA analysis

   • accurate but expensive and timely

6. X-ray fluorescence

   • based on chemical differences in individual skeletal material

7. biological features

   • age, sex