Preservation and Handling of Physical Evidence
The preservation and handling of physical evidence will depend on:
- The state of the evidence e.g. liquid, solid, latent, transient.
- The type of evidence e.g. document, firearm, wildlife trophy.
- The size of the physical evidence.
- The examinations required for that particular physical evidence.
Packaging Physical Evidence
In deciding on the best method of packing of any particular piece of physical evidence or article you should ask yourself whether the method chosen is adequate to prevent:
- Loss during transit.
- Mechanical damage from jolting or crashing.
- Obliteration by environmental conditions.
- Alteration of physical state.
How to Package Various Classes of Physical Evidence
(a) Wildlife Trophies
Unworked wildlife trophies such as elephant tusks and wildlife skins are sometimes too large to package in available containers. Always ensure that the trophy remains in the container in which it was collected. You can repackage this container into a sack, carton box or any large container. Mark the container with the relevant details. Ensure that in packaging and transporting the trophies you do not break them, deface them or alter their physical state such as colour. Ensure you note all unique marks before packaging.
Worked wildlife trophies can be packaged in plastic evidence bags because there is no danger of decomposition.
(b) Carcasses and Bush Meat
You may not be able to package wildlife carcasses and large quantities of bush meat because of their size. The best way to preserve and collect this kind of evidence is to photograph it. Ensure that when taking the photograph you capture the entire carcass and photograph it from various angles so that the species of the animal can be easily identified from the photograph.
When recovering small quantities of bush meat, package them in airtight containers and freeze them to avoid decomposition. If there are no refrigeration facilities available, take a photograph as in the case of carcasses. Where it is necessary to take bush meat samples to the Forensic Laboratory for analysis, take the following steps;
- Photograph the entire exhibit.
- Cut off a small sample for analysis and package it in an airtight container.
- Photograph the sample and entire exhibit together to demonstrate that you took the sample from the exhibit.
- Refrigerate the sample or immediately deliver it to the laboratory to avoid decomposition.
Allow blood stained clothing, shoes or other objects to dry completely at room temperature before packaging them. Do not place blood stained items in bright sunlight to dry as this will destroy DNA. When the object is completely dry package it in a brown khaki paper bag, envelope or carton box. Do not use nylon bags or plastic containers as they encourage decomposition. Only use these if you are going to refrigerate the sample immediately.
If you are collecting only the blood sample, you can use a cotton swab on wet blood. Let the swab dry at room temperature and package in a khaki envelope. Alternatively put the wet swab in a plastic airtight container and refrigerate.
Safety first. The first thing to remember when recovering a firearm is safety. Always use gloves to avoid contaminating the exhibit or erasing latent fingerprints. You may leave unfired cartridges in the magazine of a weapon, provided that you remove the magazine from the firearm. Never pick up a weapon by placing a pencil or other object in the end of the barrel as this is unsafe and may interfere with gun powder residue.
Record the serial number, make, model, and calibre of the weapon, and mark it in some inconspicuous manner that does not detract from its value. It is important to mark firearms, since duplicate serial numbers are sometimes found on different guns of the same make and general type. Do not confuse model numbers or patent numbers with serial numbers.
Place firearms in strong cardboard or wooden boxes, well packed, to prevent shifting of guns in transit. Do not strip rifles or shotguns but leave them intact, save for removing the magazine. If blood or any other material, which may pertain to an investigation is present on the firearm, place a clean paper around the sample and seal it with tape to prevent movement of the gun and loss of the sample during shipment.
Wrap recovered bullets in paper and seal in separate labelled pill boxes or envelopes. Do not attempt to clean recovered bullets before sending them to the Laboratory. Ensure that you air dry bullets recovered from a carcass. Wrap the bullets in tissue paper to avoid decomposition of the DNA of the blood on them. Washing may destroy trace evidence.
Wrap recovered cartridge cases and seal in separate labelled pill boxes or envelopes. Submit the weapon and all recovered unfired ammunition if the ballistic examiner will need to carry out an examination to determine if the weapon fired a particular shot shell or cartridge. Wrap each cartridge in paper to prevent damaging the breech clock, firing pin, or other markings by contact with other cartridge cases.
When you obtain firearms as evidence, always attempt to recover unused ammunition for comparison purposes. It may be important for test purposes to duplicate exactly the make, type, and age of the ammunition used in the crime. Do not mark unfired ammunition. You may, however, mark the box with the ammunition without marking every round in the box.
Under no circumstances should documents be marked, defaced, or altered. Do not make any new folds or make marks or notes on the document. You may make personal marks for identification purposes as small as possible on the back or other area of the document where no handwriting or typewriting is present. You should protect documents by packaging them in cellophane or plastic envelopes. Where the document is charred or partly burnt, take great care to prevent any additional crumbling or breaking apart of the burned material.