Investigations | Section 4.5

Fundamentals of Criminal Investigations

Adam J. McKee, Ph.D.

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Section 4.5: Document and Voice Evidence

For crime scene investigations containing voluminous documents, a Forensic Document Examiner (FDE) can provide valuable on-site support. The FDE can be effective in screening large numbers of questioned documents to assist in selecting representative samples that are more likely to provide useful information for a specific investigation. Similarly, the FDE can effectively screen larger numbers of existing known writing samples, e.g., forms within records available in personnel offices. The expertise of the FDE for these screening tasks can save many hours of investigator work time, limit the amount of unnecessary evidence taken for evaluation, and consequently reduce the time required for FDE examinations of the more relevant documents submitted.

Collection of Documents

Toner on documents produced from photocopiers or laser printers, correctible typewriting, stamps, glossy photograph surfaces, and other document components can adhere to plastic document protectors, resulting in damage when the items are removed from the protectors. They should not be used.

Handle documents in a manner that prevents changes or alterations of the evidence. Never fold, unfold, staple, attempt to reassemble torn paper fragments, or allow shifting of torn or shredded paper fragments collected from waste containers, etc. Collect all questioned documents found at the scene. Check pockets for paper and paper fragments in clothing worn by suspects, victims, and other persons of interest at the scene; these fragments may be useful in associating the person with other documentary evidence. Collect all tablets, notepads, spiral-bound notebooks, etc., containing visible writing or not, as these may contain pages with decipherable indentations and/or paper fragments to associate them with questioned documents. Collect handwriting samples: letters, diaries, and other existing written documents at the scene (standards); also collect requested writing samples (exemplars) from victims, witnesses, and suspects who may not be available later to render samples of their handwriting.

Collect computers, printers, typewriters, adding machines, check protectors, rubber stamps, embossers, etc., for comparison purposes, when these devices may be related to questioned documents in an investigation. Check any service documentation for these devices that may also be useful in associating devices with questioned documents. Collect paper, printer cartridges (ink, toner, and imaging drums), pens, markers, and other supplies that may be related to content of questioned documents. Never write on packaging containing a collected document once the document is inserted. Avoid altering a stain or mark in any way, other than as necessary for evidence collection (e.g., moistening a dried stain for swabbing). Always change gloves and use sterile tools when collecting a new sample. Do not cough, sneeze, or talk over any sample being collected or dried, to prevent contaminating the documents with additional DNA.

Documentation of Document Evidence

Ensure that the item has been documented as it was found. When photographing the item: Include a scale and an identification label. When possible, shoot accurately scaled photography. Take one or more location photographs that show the item where it was found. Show the relationship of the item to other evidence in the photograph. Marking Evidence When acceptable, mark evidence containers instead of evidence. Mark documents for identification as inconspicuously and unobtrusively as possible. For instance, make small, limited markings in an area not intersecting any of the document printing or writing (e.g., very small initials and an abbreviated time/date entry along a bottom corner on the back of a document). Use a pencil for markings if documents might be examined later for latent prints.

Evidence container labeling: Label a container for the object as specified by your agency (e.g., your initials and identification number, the date and time, evidence number, location, and evidence description). When selecting a container: For paper that is charred or burned, use a rigid, flat box lined with sheet cotton or similar material. Use an envelope when collecting checks, receipts, letters, reports, or other similar documents. Always use envelopes that are larger than documents collected. Evidence number: Each piece of evidence must have a unique number for identification. This number should correspond to the placard next to the evidence when photographing the items at a scene. Evidence description: The evidence description should include: Sufficient detail to distinguish each item from similar items collected as evidence. Condition of the document. Orientation of the document to prominent nearby landmark.

Label the container just before inserting evidence into them. Seal containers as soon as appropriate to avoid cross-contamination, unnecessary movement of fragments, etc. Handle documents with gloves to avoid adding fingerprints that may obscure latent prints of evidentiary value. Use thicker paper, e.g., pieces of manila folders, to scoop up documents and insert them into paper envelopes or paper box evidence containers, etc. When necessary, pick up documents by touching the smallest area possible, such as one corner. Avoid bending, folding, unfolding, stapling, or otherwise altering document evidence.

Charred Documents

Because of the fragile nature of this particular evidence, care must be exercised in picking up and packaging. The best method of picking up charred documents is to slip a thin but stiff piece of paper under the evidence and then place it in a cotton cushioned cardboard container that will allow complete protection without crushing it.

Indented Writing

This type of evidence should be handled in the same fashion as charred documents, i.e., package in a manner to prevent crushing or flattening of the evidence. Only the container holding the evidence should be marked by the investigator. Under no circumstances should pencil be applied to the evidence in an effort to make the text legible as this will likely destroy it. The best method of viewing the text is to view it with a light source held at an oblique angle to the document and then to record the message with photography.

Voice Identification

Questioned sample. In the vast majority of cases, the only equipment needed to obtain the unknown sample (telephone calls) is a good quality recorder and an induction telephone pickup coil. The victim can easily be taught to activate the recorder as the telephone rings for each incoming call.  If the call is recorded by an automatic system as is commonly found in a police or fire department, it becomes necessary to make a second or dubbed recording for laboratory analysis. This is accomplished through the use of a second recorder and a patch cord attached directly between both recorders, thus eliminating any noise occurring in the environment of the recorders. If this method is utilized, no Significant information for identification is lost. Should there be an absence of jack outlets on the original recording machine, the microphone for the second recorder may be placed in front of the speaker of the original recorder.

This is the least desirable method as the resultant tape will now contain any additional noise present in the recording site plus a loss of information that was present on the original tape. Should this seem to be the only method available, the Voice Identification Unit of the Laboratory should be consulted. for an alternate means of recording the sample.

Known Voice Samples

It is of primary importance that the context of both samples be identical. Random conversations will not be sufficient for comparison purposes. The investigator should make every effort to duplicate the questioned sample as closely as possible regarding context and conditions under which it was recorded, i. e., telephone, live conversation, or radio. Remember that while the quality of the questioned sample cannot be controlled, in many instances the quality and the environment in which the known sample is recorded can. To ensure uniformity between the samples, efforts should be made to record them in surroundings that are free from other sounds which may mask the samples. It is necessary for longer samples to have a transcription of the unknown sample. This will assist the investigator in obtaining a known sample and will also assist the Voice Identification Technician in examining the samples. The investigator should make every effort to ensure that the suspect repeats the context duplicating inflection, speed, and, if possible, the emotion shown in the unknown sample. As reading out loud produces flat, robot-like samples, it is preferable that the investigator read the sample, a phrase at a time, to the suspect for repetition by that suspect. The entire sample should be repeated for the recording three times so that it io a more natural sample of the suspect’s normal speaking habits.

It is perfectly permissible to have the investigator’s voice on the tape as well as the suspect’s voice. The tape should be prefaced with information containing the identity of the speaker, who is present, and the date and time of the recording. Known samples may be obtained — voluntarily or by court order. Should the investigator need more information on methodology, he may contact the Voice Identification Unit at the  Laboratory.

Key Terms


References and Further Reading


Modification History

File Created:  05/02/2019

Last Modified:  05/16/2019

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This work is licensed under an Open Educational Resource-Quality Master Source (OER-QMS) License.

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