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Each fingerprint examination will result in one of the following conclusions:
- The fingerprint was made by (identified/individualized to) a known source (victim, suspect, etc.)
- The fingerprint was not made by (excluded to) a known source.
- The fingerprint cannot be identified or excluded to a known source (inconclusive).
- The fingerprint is of no value to compare (not suitable for comparison) to a known source.
Perhaps the primary limitation of fingerprint analysis is that there must be a known print that can be compared to the collected print. Unless there is a known suspect or the perpetrator’s prints are found on file in one of the many databases around the world, the collected prints will likely only be used to exclude individuals from the investigation.
Another limitation is that there is no scientific way to determine the time a latent print was deposited on a surface. An examiner cannot tell how long a print has been on a surface or under what circumstances it was placed there. For example, if a suspect’s print is found in the kitchen of a murdered acquaintance, the print may or may not be tied to the murder, especially if the suspect claims to have visited the victim’s house fairly recently.
It is not possible to determine sex, age or race from a latent print; if sufficient DNA is left behind, then the party’s sex can be determined. Learn more about DNA ▸
To ensure the most accurate analysis of evidence, the management of forensic laboratories puts in place policies and procedures that govern facilities and equipment, methods and procedures, and analyst qualifications and training. Depending on the state in which it operates, a crime laboratory may be required to achieve accreditation to verify that it meets quality standards. There are two internationally recognized accrediting programs focused on forensic laboratories: The American Society of Crime Laboratory Directors Laboratory Accreditation Board and ANSI-ASQ National Accreditation Board / FQS.
In disciplines such as fingerprint examination, where testing requires analysts to compare specific details of two samples, quality control is achieved through technical review and verification of conclusions. This involves an expert or peer who reviews the test data, methodology and results to validate or refute the outcome. The Scientific Working Group on Friction Ridge Analysis, Study and Technology (SWGFAST) publishes quality assurance standards for use by forensic practitioners. These standards indicate that all identifications must be verified, whereas exclusions and inconclusive results should be verified. This involves having an expert or peer review the test data, methodology and results to validate or refute the outcome.
Reports typically will state what evidence was received, what types of examinations were conducted and the results of those examinations. Results should be worded clearly so that the end user has no difficulty in understanding the results (see “What kind of results should I expect?” above).
Once the examiner has completed their analysis and reached a conclusion, there is no interpretation required. Results clearly fall into one of the four categories.
Are there any misconceptions or anything else about fingerprint examination that would be important to the non-scientist?
Just because someone touches a surface does not guarantee that a latent print will be deposited. Here are some reasons a print may not be deposited:
- The person may be wearing gloves.
- The person’s hands may be very dry, which means there is little or no sweat or oils coating the ridges. Therefore, the ridge detail won’t reliably transfer to the surface.
- Rougher surfaces are less conducive to receiving latent impressions than smooth surfaces.
Even if a print is deposited, it may not become a useful piece of evidence. Here are some reasons why:
- It may not be discovered.
- It may not survive, due to environmental factors. For example, prints deposited outdoors in arid climates may not survive long because latent print residue is approximately 98% water.
- If a particular surface or item is collected/packaged improperly, any latent prints may be destroyed.
- The print may be found but not contain a sufficient amount of information to be useful. For example, it could be a partial print, a smeared print, or from a part of the hand for which a known print is not available.