Evidence examination, whether it is soil, body fluids, glass, hair, or even fibers, often requires a comparison of unknown samples with a known portion of the material being analyzed. Most crime scene investigators can readily recognize and collect relevant crime scene evidence; however, the laboratory has seen an increase in the number of cases lacking appropriate reference standards.

A standard is an item obtained from a known source, such as pulled head hair collected from Suspect A. Standards are used for comparison purposes to establish a link between the crime scene evidence and the known individuals or objects involved. For example, the pulled hair from Suspect A can be compared to the hair collected from a victim's clothing to determine if Suspect A can be included or excluded as the donor of the hair found on the victim.

Most disciplines in the lab require standards in routine analysis. Use the appropriate section(s) from this guide when collecting and submitting evidence to the laboratory for analysis. Quality forensic science depends on good, thorough police work.

DNA

For every case submitted requiring DNA exams, a blood or buccal (cheek cell) standard MUST be submitted from each individual involved. This includes both the victim(s) and suspect(s). If blood is submitted, use a purple capped blood tube. If a buccal swab is submitted, be sure to properly air dry the swab and place in a paper material container. Label all items (tubes, envelopes, etc.) with the source (contributor) of the standard. Standards must also be packaged separately from any unknown evidence samples.

Elimination standards may be necessary in certain instances, such as when a sexual assault occurs on bedding belonging to someone other than the victim and the suspect. The owner of the bedding must contribute a standard for elimination purposes.

If a sample just cannot be obtained, such as when a body has been cremated, a secondary standard (a toothbrush or comb as sources of DNA, for example) may be acceptable. Contact the lab for further instruction in such cases.

DNA exams will not be attempted until the lab receives all appropriate standards.

Latent Prints

Standards for print comparison are the customary 10-print card taken upon arrest of a suspect. 10-print cards may also be used for elimination purposes, as well. 10-print cards are required for a complete examination for all latent print submissions. Send a photocopy or fax of the original card only as a last resort.

When obtaining a set of inked impressions, place the prints in the appropriate spaces provided on the 10-print card, completing both the rolled print and simultaneous print portions.

Using the appropriate amount of ink is crucial to ensure the impressions are not too dark or light.

Inked palm prints are rarely submitted; surprisingly, 50% of the lab's casework involves latent palm prints. Collect these standards if the case may involve palm prints.

Firearm / Toolmark / Impression

The lab secures known test standards from a particular item of evidence in these types of cases. The criminalist obtains test bullets, cartridge cases, or shotshells from a suspect firearm during test firings, toolmarks from the tool in question, and test impressions from suspect articles, such as shoes or tires.

Once the criminalist obtains and compares standards to an unknown ammunition component, toolmark, or impression from a crime scene, they become part of the evidence which made them. They are returned upon case completion to the submitting agency, which is responsible for the preservation and storage of the test standards for future reference.

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