Evidence recovery and collection
Effective collection and packaging of evidence is critical in a forensic investigation as this contributes to the successful completion of a case. Appropriate handling of evidence should be used to:
- protect personnel from potential hazards associated with evidence (eg biohazards, sharp objects)
- protect the evidence from loss, destruction or contamination
- correctly identify the evidence (eg nature, source)
- ensure the evidence is secure and tamper-proof.
The choice of collection and packaging method depends on the type of evidence to be recovered.
The most common biological evidence found at crime scenes are body fluids (eg blood semen, saliva). The surface on which they are deposited determines the collection and packaging procedure to be carried out. Wet stains are always air-dried before packaging can take place. Bloodstained garments: different items of clothing should never be packaged in the same container and, whenever possible, the entire stained garment should be collected. The garment should be folded only enough to fit the container and ensuring that the stained area is not creased. Paper can be used to prevent transferring of the stain to other areas of the garment. Bloodstained garments are packaged in breathable paper bags or boxes.
These are generally items of small size that could be easily lost during handling (eg hairs, glass fragments, paint flakes, fibres). Once they have been located and identified, precautions need to be taken to prevent damage, contamination or transfer. Collection techniques include picking, lifting, scraping, vacuum sweeping, combing and clipping. Several tools can be used for the collection of trace evidence (eg tweezers, tape lifts, spatulas). Trace evidence should never be placed directly into envelopes or paper bags without placing the evidence into a smaller, leak-proof container first (eg glassine bindle, canister, Teflon-lined screw cap glass vial, bottle/jar). Glass fragments: if multiple fragments are present, all of them should be collected. Tweezers can be used for the collection of fragments with compatible size; only sufficient pinching force should be used to prevent damage. The glass is first placed into a paper bindle. The bindle is sealed before it is inserted into a paper or plastic bag, depending on size. For fragile fragments, the paper bindle can be placed inside a sturdy box with a close fitting and sealed lid and then into a bag.
A loaded weapon should never be packaged. Firearms should be unloaded and placed into a safe condition by trained personnel first. Firearms should be handled as little as possible to preserve other evidence that could be present (eg blood, trace evidence, fingermarks). These are usually packaged in an appropriately sized box and secured down with plastic cable ties ensuring that these do not go through the barrel. Firearms and ammunition must not be placed in the same transportation box unless they cannot be separated.
Each package must be properly sealed and appropriately labelled. Evidence labels should contain information that:
- uniquely identifies the exhibit
- says exactly where/when it was recovered
- shows details of the person who recovered it
- provides details of the person who has handled the item after it has been recovered and packaged (ie details of the chain of custody).
Consider other potential evidence types (eg bloodstained carpet, paint fragments). How would you carry out collection and packaging?
© Chris Reynolds: geograph.org.uk/profile/34693