The type of fiber (e.g. natural or synthetic, animal fiber, glass fiber, etc.)
The possible product uses for the fiber (e.g. carpet fiber, clothing fiber, etc.)
The degree of similarity between evidence fiber(s) and a fiber source
| Impounding Officer procedures | Evidence Officer procedures | Disposal |
Fibers are easily transferred between individuals and between individuals and environments. Fiber evidence can be of value in cases such as homicides, assaults, robberies, and burglaries. Research has shown that with few exceptions the largest quantity of fibers on an object is from the last person to be in contact with it. Therefore, it is advantageous to consider collecting fiber evidence from vehicles prior to continuing with a search of the vehicle interior.
Laboratory analysts examine various physical, chemical, and microscopic properties of fibers when performing a comparison between evidence fibers and a potential source. Common conclusions include statements regarding the similarity or dissimilarity of the evidence fiber(s) to the possible source or standard. Fiber comparisons cannot, however, determine the source to the exclusion of all others.
The following may be determined from fiber examinations:
|
The type of fiber (e.g. natural or synthetic, animal fiber, glass fiber, etc.) |
|
The possible product uses for the fiber (e.g. carpet fiber, clothing fiber, etc.) |
|
The degree of similarity between evidence fiber(s) and a fiber source |
Collection of Fiber Evidence
Fiber evidence can be collected in a number of ways. Table 4 lists various methods and when they are appropriate. Contact the Forensics Supervisor with questions.
Fiber Collection Methods
|
Method |
Description |
Packaging |
When to Use |
|
Adhesive lifts (not advised) |
Use fingerprint tape, cellophane tape, or other clear adhesive substrate and pat over the item. Take care not to miss any areas or allow the tape to become “overloaded.” Post-It notes may also be used for small areas. |
Stick adhesive tapes onto a clear, colorless plastic sheet (e.g. transparency film). Place into a paper envelope or bag. Fold Post-It notes in half and place into a paper envelope. |
For fibers you cannot see, or to be sure you have not missed any. Good on car seats, surfaces of clothing, and other medium to large surfaces. |
|
“Pick” method |
Using your fingers or tweezers, carefully retrieve the fiber taking care not to pinch, crush, or stretch it. |
Place the fiber into a paperfold, in a folded Post-It note, or paper envelope. |
For fibers you can see. |
|
Vacuum sweepings |
Use a portable vacuum cleaner equipped with special traps holding a piece of filter paper. Lightly vacuum the surface of interest. The goal is to collect fiber evidence that is on the surface of the object, not to clean it. |
Carefully remove the filter trap, cover with the lid or cap, and package in a paper or plastic bag. |
For fibers you cannot see, or to be sure you have not missed any. Good on car seats, sections of carpeting, and other large surfaces. |
Standards (or a possible source) are required when the laboratory is requested to perform a fiber comparison. If the possible source can be packaged and transported to the laboratory with ease, submit the entire object (e.g. clothing items, throw rugs, etc.)
If the fiber source is believed to be from a large object or one not easily transported, such as car upholstery or carpeting from a dwelling or vehicle, cut representative samples from various areas of the carpeting. Be sure to collect samples from areas that are visually different (e.g. different colored areas, faded areas due to sunlight, worn sections, etc.). Samples should be about 1x1 inch unless you see variations in the carpet that would warrant a larger sample cutting.
Package the garment, object, or sample cuttings in paper envelopes or bags and clearly label with a description of where the standard came from.
Do not package standards with evidence fibers, or allow them to be near or in contact with each other. This could allow cross contamination to occur cross- transfer of fibers between clothing of the victim and assailant may take place in incidents of homicide, assault, and other crimes against persons. It may be possible to find evidence of association between the clothing of a subject and a textile material (e.g., carpet) at a particular scene. Cloth evidence may be found along the path of a subject’s travel, into or out of a building, at a torn screen, at a broken window, or at other sharp edges. Types of fiber transfers are not always visible to the unaided eye therefore the items must be examined at the Crime Lab.
Handle clothing as little as possible. Take care to not allow the clothing of one individual to come in contact with clothing of another individual.
Clothing or other fabric that is wet, must be hung up to dry thoroughly. Place items in Locker ‘A’ or ‘B’ in the Sheriff’s Office, or Lockers, 22, 24 or 25 at East Precinct. Place different individuals clothing in different lockers.
Complete evidence labels and attach to brown bags for packaging after clothing is dry. If the clothing is not saturated to the point of ‘dripping’ and there is no chance that the bags will become wet, place the bags into the same locker as the clothing. If there is a chance that the packaging will become wet, you may leave it with an evidence officer, or in another locker, indicating on the property report the location of the packaging.
Package each item of clothing in a separate brown paper bag if they are dry. Seal the top of the package by folding and taping the opening. DO NOT staple the opening. This creates holes where fibers can escape, and may render the items as ‘contaminated.’
DO NOT package wet or damp items into plastic bags. Biological evidence decays rapidly when wet and then sealed in plastic.
Submit the original container that the articles were transported in as evidence.
Complete the Forensics Services Request, place the blue and yellow copies into the basket in the Evidence Processing Room.
Mark the packaging with Bio Hazard sticker if appropriate.
Complete the property-evidence report.
Place the items into an evidence locker. Note location on the property-evidence report.
Place the yellow and green copy of the property-evidence report in the property-evidence basket in the Evidence Processing Room.
STORAGE
Ensure proper packaging; refer to the example board in the evidence processing areas.
Place one barcode on the item and the corresponding barcode on the property receipt.
Place the item in a location best suited to the size of the article, and area specified by the evidence room guide.
Using the barcode reader, scan the location of the shelf, and then scan the barcode affixed to the item.
Place item in numerical order by case number.
Upon authorization or disposition of the case, see General Disposition of Items.
Revised 11/05/03