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Latent Prints

Friction ridge skin consists of ridges and furrows and is present on the palm side of the hands and soles of the feet. It possesses two important properties: permanence and uniqueness. With the exception of injury, the friction ridge skin forms before birth and does not change naturally until after death.
 
An impression from friction ridge skin may be left behind when an individual touches, grabs, or walks barefoot on a surface. These unintentional impressions are referred to as latent prints. Latent Prints are typically invisible to the eye without physical and chemical enhancement and can be recovered from a variety of substrates including: Porous, Non-porous, Semi-porous, and Adhesive surfaces.
 
When latent prints are developed through applied physical and chemical processing techniques in the laboratory, the areas are photographed (using high resolution RAW images) and digitally stored for the examination process. It is important to note that a complete impression is not required for the impression to be of value. A partial impression that is of high clarity and quantity may be enough for preservation and comparison purposes.
 
Analysis, Comparison, Evaluation, and Verification (ACE-V) methodology is a structured and systematic guide used for comparing friction ridge detail. From this, one of the following evaluations will be reported for latent print comparisons:  match/identification, no match, inconclusive, or exclusion. Latent prints that are of sufficient quality and have not been identified using known prints can be entered into the Automated Biometric Identification System/ Western Identification Network (ABIS/WIN) and Federal Bureau of Investigation/ Next Generation Identification (FBI/NGI) systems.
 
The latent print section performs the following duties:

1. Process physical evidence for the presence of ridge detail and preserve ridge detail for further analysis.
• Latent print processing consists of developing and recovering latent prints from items of evidence.
 
2. Compare ridge detail to known ridge skin from individuals associated with the case.
• Any recovered latent prints will be reviewed by an analyst. The analyst then decides if the prints contain enough information for identification through the comparison process. Many areas of ridge detail preserved during evidentiary processing will not contain enough characteristics to establish identity.
 
3. Any unidentified ridge detail may be entered and searched through the automated search process.
• Automated Biometric Identification System (ABIS), which is a computer system that searches prints against databases of known fingerprints.
 
4. At a minimum, routine analysis will be performed on items submitted where Latent Prints is the only service requested. The laboratory will seek to identify the individual(s) of interest at a minimum of once per submission, the processing and comparison for that case may cease at the analyst’s discretion. If after analysis has been completed it becomes apparent that items not tested will require testing then, upon re-submission, these items will receive top priority at the laboratory.
 
Physical Evidence:
Physical evidence is anything collected at the scene of a reported crime. Various items can be conducive to latent print recovery.
Such items include, but are not limited to:
• Glass (bottles, pipes, windshields, mirrors, etc.)
• Plastic (scales, bags, baggies, plastic wrap, bottles, etc.)
• Paper (receipts, notes, etc.)
• Smooth metallic items (spoons, knives, weighing trays, firearms, etc.)
• Tape (smooth and sticky sides)
 
Considerations should be made regarding evidence that needs to be analyzed in other sections.
Controlled Substance: Faster results will occur when separating the items needed for analysis in each section (controlled substances and latent print examinations). At a minimum on Items submitted for both Controlled Substances and Latents Prints; latent print processing will only be performed on items tested for controlled substances where the results were positive.
Firearms: Latent print examinations will occur prior to any firearms analysis. Due to normal handling during firearms analysis, latent print recovery cannot be done after this occurs
Biology/DNA: When an item requires both latent print and DNA analysis, biological screening is typically done prior to latent print examinations. Typically, smoother items (blades, slides of guns, etc.) are better for latent print recovery and textured surfaces (grips, handles, etc.) are better for contact DNA recovery. Some items are better suited for one examination or the other and will not have both types of processing performed, even when requested. The following items will not routinely have both contact DNA and latent exams conducted:
  • Casings/bullets – only latent print examination will occur
  • Condom wrapper – only latent print examination will occur
  • Unopened beverage containers – only latent print examination will occur
  • Beverage containers likely drank directly from – both exams are possible. If probative findings are obtained from either latent prints or DNA, the other analysis will generally not be performed
  • Cigarette packages – only latent print examination will occur
  • Cigarette butts (smoked) – only DNA analysis will occur
Latent Print procedure manuals are located in a tab under the Quality Assurance section of the webpage. They can be accessed by clicking here.
Latent Print Collection Guidelines
 
ALWAYS WEAR GLOVES WHEN HANDLING EVIDENCE!
 
Field Processing:
  • First perform a visual examination of the item/area using a flashlight. If the contrast is clear enough the latent print should be photographed before any further processing is attempted.
  • Take close-up photographs using a scale and identifier (example: L1).
  • Dust with fingerprint powder (Don’t over powder).
  • Use lift tape (avoid air bubbles) and apply the lifted area onto the appropriate side of the lift card.
  • Use a contrasting background (example: Black/Gray prints should be placed on white lift cards).
  • Fill out the case information including the case number, date, identifier for the officer who lifted the print, location, and orientation of the latent print.  
    In some instances, latent fingerprints can be developed at the crime scene. Searching with a flashlight and then dusting with powder is a quick and simple method for processing multiple items and areas at a crime scene. If a print is hard to photograph, do your best to lift the print. If a print will not lift, photography might be the only means of documentation.
     
    Note: If any item of evidence is to be submitted to the laboratory for latent print processing, it is best not to attempt any field processing prior to submission. Powder and other on-scene processes may interfere with the techniques utilized in the laboratory.  
     
     
    Photography: All close-up photographs should include a scale and identifier. Keep the film plane parallel and fill the frame to maximize photographic detail.  Submit all photographs and lifts from field processing to the laboratory via the Request for Laboratory Services form. All digital photographs must be submitted on a CD or DVD and as an item of evidence.
     
    Note: Keep in mind, if you do not have adequate photographic equipment available to you (i.e. high resolution, digital cameras capable of capturing in TIF or RAW format) a lift may be better than a low resolution photograph.
     
     
    Packaging:
    • Tape-seals must accompany the outermost packaging of any item.
    • Paper envelopes, brown paper bags, and cardboard boxes are adequate for most items.
    • Package non-porous items separately (properly secure if necessary) to minimize movement and contact for the best preservation of latent print evidence.
  • All porous evidence can be grouped and packaged together.
  • All lift cards should be packaged together. 
     
    Known Prints:
    Known prints or exemplars are impressions from an individual intentionally recorded in a controlled manner using ink or electronic scanning methods. The most common form is a ten print card consisting of each finger being rolled nail-to-nail, slap impressions of all fingers, and appropriate identifying information for the individual being fingerprinted. It is important for the submitting officer to verify if an individual has known prints on file with the State of Alaska and to provide any identifiers (APSIN number, FBI number, name, date of birth, social security number, etc.) on the Request for Laboratory Services form. If an individual does not have known prints on file, the submitting officer will need to collect them and submit them as an item of evidence.
     
    When recording palm prints, use an ink roller to coat the entire area of the palm (including below the wrist bracelet, and the blade or “writers palm” area) with an even and thin layer of ink. Roll the palm onto a piece of paper using a cylinder starting from below the wrist bracelet (be sure the center of the palm is captured in the impression).
     
    Note: It is important NOT to over ink the fingers/palms when recording known prints as excessive ink may fill in the fine detail present in each impression.

For further information on commonly asked questions regarding the science of fingerprints, latent prints or related topics please refer to these online resources;

https://www.fbi.gov/services/cjis/fingerprints-and-other-biometrics

http://onin.com/fp/

http://www.clpex.com/

https://www.nist.gov/topics/forensic-science/friction-ridge-subcommittee

Or you may submit your questions directly to the laboratory by emailing the Physical Section Supervior. The contact information is available on the main lab page.