1. Forensic Update Nicola Clayson
Lead Scientist – Sexual Offences and Damage
SPA Forensic Services, Edinburgh

2. Outline the work undertaken at the forensic laboratory.
New techniques.
Casework considerations.

3. Scientific Investigation of Sexual Offences
Semen
Vaginal Material/Cellular Material
Blood
Saliva
Faeces
Urine
Fibres/Hair
Damage to clothing

4. Acid Phosphatase (AP) Test for seminal fluid
Strength & speed of reaction

5. Microscopic Examination
The spermatozoa found are scored using the following guidelines:
+ heads - hard to find
++ heads - easy to find with some heads in some fields
+++ heads - many or some heads in most fields
++++heads - many heads in every field
The presence of tails is also noted.
2µl aliquot of pellet
Differential stain (H&E)

6. DNA Profiling – SGM +

7. DNA Profiling – Globalfiler

8. 24 areas, including mini-STRs
Better performance on inhibited and low-level samples
Twice as sensitive

9. Semen Persistence Vagina up to 7 days Anus up to 3 days
Mouth up to 2 days
Skin subject to abrasion/ reduced by washing
Clothing AP until washed
Spermatozoa after washing
All relevant swabs should be taken in line with the FFLM guidelines.
Guidelines are reviews every 6 months, critical as DNA chemistry changes.

10. Azoospermic and Oligospermic Semen
AP reaction
Choline
DNA profiling
Semenogelin

11. Case Example
Girl walking through park and befriended by young male. They spend a couple of hours together chatting. The male then takes the girl to a secluded area removes her lower clothing and rapes her.
Incident reported to Police and girl is medically examined less than 12hours later.
Girl has not washed and no previous intercourse.
Biology Exam
Vaginal swabs from girl - semen present and submitted for DNA analysis
DNA
Male DNA profile obtained. If no suspect, profile can be uploaded to National DNA Database. If further enquiries lead to a suspect a buccal swab can be taken for DNA analysis for direct comparison with profile already obtained.

12. “Vaginal” Material Penile Swabs Condoms Nail / finger swabs
Clothing e.g. men’s underpants
Mixtures e.g. bedding, inserted objects

13. Case Example Female child complainer.
Accused lived next door. Numerous allegations made against accused in previous years.
Complainer stated that accused had digitally penetrated and raped her.
Accused denied any sexual contact.
Biology Exam
Internal and external vaginal swabs from complainer – no semen found.
Clothing submitted had been washed – extracted crotch of complainer’s pants – 10 sperm heads found. Submitted for DNA.
DNA
DNA from sperm heads on pants matched accused.
N.B. Case dependent!

14. Case Example
Uncle had been sexually abusing his niece over a long period of time. When it was reported to the police the last incident had been over 3 weeks previous therefore no medical swabs taken
The girls bedding was seized as it hadn’t been washed for over a month.
Bio Exam
Sheet screened for semen using AP reagent. Two areas of semen staining found and submitted for DNA.
DNA Exam
Both areas of staining were a mixture of the Uncle and his niece
Issues
Uncle has stayed over at his brothers house (niece’s father) a few times over the last month and had been given his niece’s bed to sleep in.
We are unable to say when the semen was deposited in the bed, other than since it was last washed.
We are unable to say whether the stain could be due to a semen stain deposited on top of the sheet where the niece’s DNA was already present rather than an actual mix of two body fluids

15. Case Example
Young boy at his friends house is left alone with his friends older brother. The brother forces him to perform oral sex on him. The brother ejaculates in his mouth.
The victim runs home and brushes his teeth and rinses his mouth out with water a few times.
He then tells his parents and it is reported to Police and medical exam carried out. The suspect is found next day and is medically examined. He hasn’t washed.
Biology Exam
Cells on penile swabs - submitted for DNA. No Saliva test carried out.
Victims toothbrush is taken and examined. Traces of semen found.
DNA Exam
Mix of victim and accused DNA from accused penile swabs.
Accused DNA from semen found on toothbrush

16. Semen Considerations
When was the semen deposited (bedding, underwear).
Effect of washing (traces of semen found on jeans taken 1 year after the incident date).
Contact with items potentially stained with semen (washing basket, washing mahine).

17. Saliva Oral sex - penile swabs / condoms Licks, sucks and bites
Spitting
Chewing gum

18. Saliva - High concentration of Amylase
Tests for Saliva
Saliva - High concentration of Amylase
Not everyone produces amylase, and it is present in other body fluids.
Phadebas test – indicator only, not conclusive
Microscopy – mouth cells
DNA
Amylase – enzyme in saliva. Not all people secrete, and individuals secrete differing amounts throughout day – vag material, semen and faeces at lower levels
Microscopy – identify cells
DNA analysis

19. Other Items
Tampons
Condoms
Clothing
Bedding
Objects inserted
Toothbrushes

20. Touch samples / contact traces
Generally no suspect cases – no other evidence
Swabs of waistbands, buttons / zips, anywhere complainer was grabbed
Elimination samples from anyone involved

21. LASER MICRODISSECTION (LMD)

22. Damage to Clothing Important in consent cases
Age of damage – old, recent, not determinable
Physical fit
Type of damage
Compare to weapons
Amount of force? – v. difficult, many variables

23. Scenes/ Larger Items Clothing Bedding Seating Floors Cars
These items can be submitted to the laboratory for exam.
Other items may require scientists to examine them in situ.