Latent Print Evidence Collection Guidance...


Latent Print evidence can typically be divided into two categories: Porous and Non-porous.

DO Submit all porous evidence to the laboratory for latent print processing. No "field processing" of this type evidence is required or desired.  Field expedient processes such as iodine fuming or dusting with magnetic powder should never be used.  They will fail to develop many latent prints and are far inferior to laboratory procedures.

DO Package porous evidence as conveniently as possible.  Wear gloves when handling the evidence.  Allow wet or damp evidence to dry before sealing and mailing to the lab.

DO wear gloves... but maybe not for the reasons you think!  Wear gloves primarily to keep your hands clean.  Assume that any relatively smooth area your gloves touch will destroy identifiable latent prints on non-porous or semi-porous surfaces.  When you are handling evidence without poison/drug or biohazard dangers, cloth gloves are more comfortable than surgical type gloves because your hands won't sweat.  Keep all gloves clean.  Touching a contaminated surface (such as scratching your oily nose) will result in fabric impressions from the gloves (or your own fingerprints when thin surgical gloves conform to your underlying friction skin ridges) later developing on the evidence... possibly obscuring an otherwise identifiable latent print from the perpetrator.  Clean gloves will not harm latent prints on papers or other porous surfaces.  If you keep cloth gloves just for handling evidence, keep several pairs so you can rotate and launder them routinely.  When you see investigators in the movies pick up a firearm or drinking glass with their hand covered by a handkerchief... you are seeing an example of how to almost certainly destroy the perpetrator's latent prints on those smooth, non-porous surfaces.

DO "Field process" all non-porous items by "super glue fuming" at the earliest possible time. Handle the evidence no more than necessary prior to the super glue process.

No further "field processing" is required or desired.  Send the evidence to the laboratory.  Click here for the latest super glue fuming hints.

DO "Super glue fume" non-porous drug evidence items in almost all instances prior to packaging. All types of drug evidence can be super glue fumed prior to placing in a heat sealed evidence bag. (The chemical composition of the drug is not affected by super glue fumes.)

DO Submit all latent print lifts to the laboratory and allow latent print examiners to determine what lifts are suitable for identification.

DO Avoid unnecessary writing or marking on surfaces to be processed for latent prints. When possible use a pencil for marking porous items. Also avoid taping or sticking labels on the surfaces to be processed for latent prints.

 DO Photograph all latent prints visible at the crime scene. Pay special attention to footwear impressions that may be in dust or dirt. Include a scale in all photographs.

DO Utilize an electrostatic dustprint lifter to preserve footwear impressions found in dust or dirt on surfaces such as paper, floor tiles, walls, carpets, etc. (Collect the impression after photography.) Place each lift containing the impression in a separate box or container (such as clean pizza boxes or photo paper boxes). The lifts should be placed with the impression "face-up", taped on two edges then the lid should be closed and sealed to prevent the lift from attracting additional dust particles not related to the impression.

DO Utilize dental stone to obtain casts of footwear or tire impressions at the crime scene. Do not clean the casts, that will be done at the laboratory. Make sure the cast are completely dry then, package them securely to avoid breakage during shipment to the laboratory.

DO Photograph the footwear or tire impressions at the crime scene (90 degree angle with a scale, etc.) and forward the film to the laboratory along with any casts or dustprint foils obtained.

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