This document provides evidence collection guidelines for the following types of evidence. Your agency's policies may vary. Please check with your supervisor if you have any questions.
Blood that is in liquid pools should be picked up on a gauze pad or other clean sterile cotton cloth and allowed to air dry thoroughly, at room temperature. It should be refrigerated or frozen as soon as possible and brought to the Laboratory as quickly as possible. Delays beyond 48 hours may make the samples useless.
Request that pathologist obtain the sample directly from the heart into a yellow (ACD) or purple stoppered vacutainer (some labs request both). In rare cases when no liquid blood is available, ask pathologist to collect a section of liver, bone, and/or deep muscle tissue and freeze for typing. In such cases, proceed also with collection of a secondary standard as described below.
Blood Samples From Live Individuals
For typing purposes, have sample drawn into yellow and purple stoppered vacutainers. Note these are distinguished from the BA tubes which have grey stoppers.
If the victim is injured to the extent that a transfusion is necessary, make an effort to obtain or begin necessary procedures to obtain the pre-transfusion sample collected by the hospital. These samples are not retained for long periods by the hospital, so it is important to act promptly. Also, make sure that some bloodstained garment worn by the individual has been air dried and frozen to serve as a secondary standard.
(Obligation under People vs Nation and Hitch that a reasonable and good faith effort be made to preserve perishable evidence)
Stains and Controls
Consider special handling of non-absorbent items on (metal or plastic). Any condensation from thawing could disturb or destroy such evidence. Such items should be kept at room temperature and submitted to the lab as soon as possible.
Liquids (generally standards)
Windows are frequently broken in burglaries, headlights in hit-and-run cases, and bottles or other objects may break or leave fragments on personal belongings of suspects involved in various types of crimes.
Paint evidence is frequently encountered in hit-and run cases, on tools used by burglars, and occasionally in other types of cases.
The search for flammable fluids in arson cases should include a thorough examination of the entire fire scene. This should extend to areas where no burning occurs, since flammable fluids may have been placed in other locations where ignition failed.
Traces of flammable fluid may be found in cans at the fire scene in arson cases. Mattresses, rugs, upholstery, wallboard, and other objects at the scene may also contain fluids which can be separated and identified in the Laboratory, even though these objects are partially burned. Wood upon which such fluids have been poured and ignited may still contain detectable traces of the liquid, if the wood has not been completely charred by the fire. Even where a large and hot fire has occurred, traces of such liquid are sometimes found where they have seeped into the ground through cracks in the floor or flowed under baseboards and sills.
While most flammable fluids commonly used have characteristic odors, some substances commonly available are almost odorless and quite easily escape detection. These include some alcohols, deodorized kerosene, charcoal lighter fluids, and others.
It is possible, in many cases, to isolate flammable fluids from various, partially burned articles through means of gas chromatographic analysis and other studies to determine the type of flammable fluid present. Normally, however, the manufacturer or brand name of the material cannot be determined.
Tool marks are encountered most frequently in burglary cases but may also be found in other types of crimes. The evidence consists of striations or impressions left by tools on objects at the crime scene and various types of tools found in the possession of suspects. In other cases, it is possible by means of physical and other comparisons to prove that parts of tools left at crime scenes were broken from damaged tools found in the possession of suspects. In many cases, it is possible to identify the specific tool which made the questioned marks by means of a Laboratory comparison of tools and marked objects. In some instances, it is also possible to prove that marks of various types on tools were produced by objects which they contacted at crime scene.
The Laboratory handles the analysis of marijuana and other drugs and medicinal preparations which may be involved in criminal cases or found in the possession of subjects involved in various crimes.
Each sample of material recovered should be placed in a paper container, which can be sealed and marked. Be sure to properly seal as loose material, particularly in the case of marijuana, can leak and spill. Some drugs, like PCP, should be packaged in heat-sealed KAPAK bags.
Medicinal preparations found in prescription boxes or bottles should be left in these containers which can be sealed and marked. The information on the prescription label may be of assistance to the Laboratory.
By means of chemical tests, most controlled substances and common drugs can be identified.
Many pills, tablets, and other medical preparations are very difficult to analyze and identify unless either large quantities are available for testing, or some clues are present as to the general type of material they contain. In all cases where prescriptions are involved and the drug store and prescription numbers are known, a check of possible container content should be made at the drug store named on the label. With this information, the Laboratory will often be able to determine whether or not the contents of the containers are the same as the material described.
While controlled substances can be identified in routine cases, the Laboratory does not normally attempt to identify all medicinal preparations which may be encountered in criminal investigations. Unless specific instructions to the contrary are received, such materials are usually tested only for common preparations and their possession may violate of the law.
All evidence of this nature should be brought to the Laboratory in a sealed package.
All questioned documents involved in a particular investigation should be submitted to the Laboratory for examination. This is important since questioned documents are identified by a comparison of similarities, plus an absence of divergences or dissimilarities. In order to make an identification, sufficient handwriting, typewriting, or other evidence must be available on which to base an opinion. This means that all questioned material is needed, as well as sufficient exemplars or known specimens.
It is very important to have sufficient handwriting exemplars for comparison with the questioned document. One or two signatures on a suspect's driver's license or a draft card, in many cases, does not contain sufficient individual characteristics on which to base a conclusion. In some instances, such an examination may substantiate a suspicion and this should be considered as an investigational lead. To support this, it is necessary to obtain and examine additional standards.
Collected specimens that were made in business transactions such as receipts, promissory notes, credit and employment applications, letters, booking card, and fingerprint card signatures are writings that, in most cases represent the individual's most normal writing. It is significant in many cases that these writings be of the same date as the questioned document. It is important to obtain request specimens from a suspect at the first interview; the suspect may be uncooperative at a later date.
The conditions surrounding the preparation of the questioned document should be duplicated as nearly as possible when the request exemplars are obtained. If yellow-lined paper and blue ink were used to produce the questioned document, the same or similar color and type of paper and instrument should be used. If the suspect document is a threatening letter and the note is either handwritten or block lettered, the same style should be requested from the writer. Have subjects write their names and addresses several times and brief personal histories. This should be removed and another sheet of paper furnished. Dictate the exact words and numbers which appear on the questioned document. this should be done at least 12 times, removing the specimens from the writer's view as they are produced. If it is a check case, the specimens should be taken on blank checks or slips of paper of the same/appropriate size. The number of specimens necessary for an identification in any specific case cannot be determined; therefore, at least twelve specimens should be obtained for each questioned document.
When securing typewritten exemplars, several copies of the questioned documents should be made on the suspected machine using light, medium, and heavy touches. At least one copy should be made with the ribbon removed from the machine, or the ribbons set on stencil, and the keys allowed to strike directly on a sheet of new carbon paper, which should be inserted on top of the paper used for the specimen. This provides clear-cut exemplars of any machine's type face, showing disfigurations in type characters. Always type the exemplars on the same type and color of paper as that used on the questioned document.
Where examination and decipherment of charred paper is involved, great care must be taken to prevent any additional crumbling or breaking apart of the burned material. Normally it should be placed on top of loose cotton in a box and delivered in person to the Laboratory. No matter how it is packaged, such material will be damaged if attempts are made to ship it by mail.
In addition to handwriting and typewriting comparisons and the decipherment of charred documents, many other related examinations can be conducted by the Laboratory. These include, but are not limited, to:
This information was adapted from the California Commission on Peace Officer Standards and Training's workbook for the "Forensic Technology for Law Enforcement" Telecourse presented on May 13, 1993. Please see the acknowledgments.