Assault cases

Question 1

Chemical evidence in assault cases

Answer 1

In sexual assault cases, offenders try to obscure the biological DNA evidence.
This may involve the use of polymer or oil based materials.
The use of these substances produce their own associated trace evidence.
The detection and identification of such residues can provide valuable forensic evidence in court

Question 2

Signficance of evidence

Answer 2

condom leaves traces
unused packages as well

Question 3

Components of condoms

Answer 3

Majority of Condoms are made of natural latex rubber (contain latex proteins).
Other materials such as polyurethane may be used as alternative materials.
All types contain fine powders (talc), lubricants and / or spermicides ( nonxynol-9)

Question 4

Lubricants

Answer 4

According to these categories lubricants consist of 4 types.
Silicon based. For example, polydimethylsiloxane (PDMS).
Polyethylene glycol (PEG) and propylene glycol (PG)- based.
Oil based (petroleum grease).
Water-based (glycerin).

Question 5

PDMS

Answer 5

PDMS is the most common condom lubricant
It is not absorbed into the latex sheath
It is not absorbed into the body
It is not degradable in the body

Question 6

PEG

Answer 6

It is a clear viscous odorless liquid.
It is a simple straight chain polymer (–CH2CH2O–).
It is water soluble
It can last on mucus tissues for a number of hours before being fully absorbed

Question 7

PDMS and PEG value

Answer 7

persist on skin and mucous. PDMS detected in skin swabs. body secreations dont mask PDMS.
PEG and PG absorbed into skin and mucous.
polyethene glycol can be detected by IR and HPLC/MS

Question 8

Sample prep

Answer 8

swabs retained up to 3 months
Hexane is used to extract PDMS
methano is used to extract PEG
dicholormethane to extract spermicides

Question 9

Analytical Techniques

Answer 9

GC-MS,
HPLC-MS,
NMR,
RAMAN,
Pyrolysis GC /MS
Infrared fourier transform spectroscopy