Crime Scene to the Laboratory Flashcards
Factors that affect the transfer of fibres
- Nature of Contact
- Shedding ability of the fabric
- The persistence of these fibres on other types of fabric
Types of transfer of firbe
- Primary
- Secondary
- Tertiary Transfer
Why Collect Fibre Evidence from Crime?
- Fibres from the suspect’s clothing and from his textile environment could be left on a victim’s body
2.Fibres from the victim’s clothing and textile environment adhere to the suspect’s belongings.
Fibre evidence used to
- Link a suspect to crime
- Provide investigative lead when suspect is unknown
- Provide reconstruction information
What are the general guidelines for processing the crime scene?
1.Maintain crime scene perimeter security
2.Access limited to the crime scene processing team
3. Designate areas where trash and equipment can be stored.
4. Keep traffic patterns to a minimum during the actual scene processing.
5. The command centre should always be located outside the primary perimeter of the scene.
What are the main evidence collection techniques?
- Hand Retrieval
- Tape Lifting
- 1:1 Tape Lifting
- Combing
- Vaccum Sweeping
- Scrapings
What is hand retrieval?
Hand retrieval method is when fibres are picked up using tweezers and forceps and placed a bindle (small piece of paper) that is folded such that they will not be lost.
Disadvantage of hand retrieval method?
Ensuring that the fibre is actually transferred from the object of interest to a secure package.
Tape Lifting method is
most effective and common method when tape is used to repeatedly touch on evidence and pick up fibres that aren’t seen by the eyes.
How do you collect tapes from tape lifting?
- heat-sealable or ziplock clear polyethylene bag
- glass microscope slide, flexible carrier
1:1 Taping method is
which one area of taping precisely represents one area of the surface from which fibres are removed. as a result, tapes are placed all over the evidence to get a full idea of the potential fibres that could be present.
Disadvantage of the taping method?
Methods like 1:1 taping can be labour intensive and time consuming.
What is the combing or brushing method?
This method is where a comb or brush is used to remove trace evidence from hair.
What is vacuum sweepings?
A vacuum cleaner with a special forensic trap that holds a paper or fabric filter that collects trace evidence.
What is the scrapings method?
Used to remove trace evidence, clothing from buried or decomposed bodies may need to be scraped.
What should labels have?
- a description of the item
- an item number and case number
- date and time collected
- the name of the person who collected the item
How to minimise contamination?
Always keep witnesses, victims, and suspects separated until trace evidence and/or clothing has been secured.
Different officers should be involved in the removal of the victim’s clothing and in the collection of suspect clothing.
If at all possible (if no drying needed), an item collected at the scene should be packaged and sealed at the scene
Separate collection materials or kits should be used for suspect and victim items- prevents cross contamination.
Investigators should wear PPE like disposable gloves.
How to classify trace evidence found on the scene?
- the scene
- the victim
- the perpetrator
- misc
What are miscellaneous files in fibre trace evidence?
encompasses loose particles that have been moving from surface to surface for some time where the source of the fibre will never be known
How is fibre evidence collected from fingernails?
Should be scrapped or clipped to collect trace materials
