GLASS AND PLASTIC
Also See Plastic And Tape Evidence
| Collection of standards | Impounding Officer procedure | Evidence Officer procedure | Disposal |
Glass is one of the more important types of physical evidence that is commonly overlooked. Glass is frequently encountered in burglaries and hit and run cases, and glass fragments may be found adhering to garments, shoe soles, or other property belonging to the suspect(s).
Glass evidence
cannot be individualized to a single source, however, there are some instances
where two fragments can be physically matched together and a common origin can
be conclusively established.
Glass examinations may reveal the following:
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Whether or not evidence glass is similar to glass from a known source |
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The type of glass (e.g. tempered glass, container glass, etc.) |
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The direction of force (from inside or outside) used to break a window |
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The order of shots fired into a window or windshield |
Consider that large glass pieces may have latent fingerprints present and the broken edges of glass may have other trace evidence present such as blood, hair, or snagged fibers.
Collect and submit all glass pieces if you believe numerous glass pieces were from the same object (e.g. a window, a bottle, vehicle headlights, etc.) and request the laboratory to attempt a physical match.
Package glass pieces from different locations into different containers, clearly marking the outside packaging as to the location and description of the evidence.
Label large glass pieces with orienting marks (e.g. up/down, inside/outside) when applicable.
Collect and package a large glass piece in a rigid container such as a cardboard box. Protect the broken or fractured edges of the glass from any additional damage or breakage. Please protect glass if it is being submitted for fingerprint processing.
Small Glass Pieces
Depending on the size, glass pieces can be packaged in envelopes, bags, or in paperfolds. For very small glass particle(s), place the particle onto the adhesive of a Post-It note and use a pen to circle around it. Fold the note in half, covering the glass particle(s), and then put the folded Post-It note in a paper envelope.
Glass pieces that are a little bigger can be packaged in envelopes or bags, then secured in a padded envelope to protect from further breakage or injury to those handling the evidence.
An individual who breaks a window with force may have very small particles of glass on his/her clothing. It is not uncommon to find minute glass particles on the soles of shoes, the tops of shoes, and the cuffs or lower portion of pants.
Collect such clothing items, taking care not to shake or handle the clothing more than necessary. Doing so may dislodge these small glass particles. If the clothing is not stained with biological material (e.g. blood), package in a plastic bag carefully sealing all possible openings. If the clothing is stained with biological material, allow the clothing to air-dry on a clean, dry surface and package in a paper bag.
A comparison of evidence glass to a possible source requires the submission of glass standards. If possible, submit the entire item in packaging that reduces the chance for further breakage.
Large windows may require a sampling of glass from several different spots, as there may be variation of physical properties even within a single glass pane.
Vehicle windshields and some structural glass may be double paned, meaning that two different panes of glass are present. Standards must be collected from different areas on both glass panes. Package the standards from each pane separately.
For window glass standards, collect the glass that is still adhering to the window frame when possible. Collecting glass standards from the ground increases the likelihood of introducing contaminant glass into the standard.
Package glass standards similar to the guidelines discussed above in “Collection and Packaging of Glass Evidence.”
Glass and plastics are used in a wide variety of modern products. These articles may be broken and become evidence in various types of criminal investigations. Windows in burglaries, headlights and plastic parts of automobiles in hit-and-run accidents, and bottles in assaults may be broken and fragments left at the crime scene or on garments. Don’t attempt to reconstruct items. This may obliterate fine microscopic details used in comparison.
Package shoes and clothing of suspects as well as other objects that may be contaminated with glass separately.
The suspects' hair can be combed over white paper to recover any glass particles that may be present. Fold the paper so that it prevents loss of the glass particles, and package in a paper envelope, or bag.
Glass at hit-and-run scenes should be collected because more than one type of glass may be present. Take note that vehicle windshields are constructed of laminated glass and control samples of both inside and outside glass should be taken.
All glass at a scene should be collected if a fracture match, direction of force or sequence of breakage examination is requested.
Tempered glass is common in glass doors and automobile side and rear windows. The diced breakage of this glass into small rectangular beads makes fracture matching impractical. However, several pieces should be collected for comparison of physical property with evidence glass.
An individual who breaks a window with force may have very small particles of glass on his/her clothing. Collect the clothing items, taking care not to shake or handle the clothing more than necessary. If the clothing is not stained with biological material package in a plastic bag carefully sealing all possible openings. If the clothing is stained with biological material, allow the clothing to air-dry by lying in the bottom of a locker on brown papers.
The same collecting and packaging procedures are used for plastic evidence as for glass evidence.
Package glass and plastic from different locations separately. Place small glass fragments in folded paper packages, and then in envelopes. Seal and mark. Place large glass fragments in bags or boxes but separate individual pieces with newspaper to prevent breakage and damage to edges.
Complete the evidence tag and attach it to the packaging.
Complete the Forensics Services Request. Place blue and yellow copy in basket in the Evidence Processing Room.
Complete the property-evidence report..
Place the item(s) into an evidence locker. Note the 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 item, and area specified by the evidence room guide.
Using the barcode reader, scan the location of the shelf and then scan the barcode that is affixed to the item.
Place the item in numerical order by case number.
Upon authorization or disposition of the case, see ‘General Disposition of Items.'
Revised 11/05/03