Fingerprint identification is an examiner’s assessment of how the details in a questioned print compare with a known exemplar. Published friction-ridge standards describe how an examination, conclusion, and written report can be handled, but they do not make every identification infallible or prove that a particular laboratory follows the same procedures. A database search candidate is a lead for examination, not the examiner’s final conclusion. The actual images, comparison, conclusion, report, and laboratory procedures matter.

How an examiner compares fingerprints

A questioned latent is the friction-ridge impression being evaluated, such as a print recovered from an item. An exemplar is a known-source impression used for comparison. Under the published ASB Standard 015, an examination proceeds through three broad stages:

  1. Analysis: assess whether the questioned impression has enough usable detail for the proposed examination and document the observations.
  2. Comparison: examine similarities and differences between the questioned impression and the exemplar.
  3. Evaluation: consider those observations together and reach a conclusion within the examiner’s procedures.

Print quality and the detail available for comparison matter. The standards reviewed here do not set one universal number of matching ridge points that automatically establishes an identification. A lab may have its own procedures and criteria; ask for the version that applied to the examination rather than assuming every lab uses the same rule.

An automated AFIS or ABIS search may return candidate prints to help an examiner decide what to compare. A candidate is not itself a final identification. The FBI/Noblis study describes database candidates as subjects for further examination. The examiner’s comparison and stated conclusion are separate steps.

What the conclusion does—and does not—say

The final 2025 ASB Standard 013 describes five qualitative conclusion categories: source exclusion; inconclusive with dissimilarities; inconclusive; inconclusive with similarities; and source identification. These are not five numerical probabilities.

Under that standard, “source identification” is an expert opinion that the observations support the same source substantially more strongly than a different source. It does not mean that the examiner has excluded every other possible source, that error is impossible, or that the result is “100% certain.” The report standard also says the presence of ridge detail on an item does not establish the print’s significance or time frame of deposition. That finding alone does not show when the impression was made or establish that its source committed an offense.

ASB 013 is a published consensus standard, not proof that a particular police or private lab adopted it. The standard describes its own scope; check the laboratory’s manual and the date of the examination before treating a published procedure as the lab’s governing practice.

What accuracy research can tell you

Studies have recorded both mistaken identifications and mistaken exclusions under the conditions studied. The 2011 FBI/Noblis study examined selected image pairs with participating examiners. A 2025 NIJ-sponsored study abstract reports decisions on selected comparisons and describes variation among examiners. These findings show why the work should be documented and reviewed; they do not give a national error rate for every lab or tell you the probability that a particular case conclusion is wrong.

Records to discuss with a lawyer

Ask counsel to identify the exact conclusion and review the records that explain how it was reached. Depending on the case and what can lawfully be obtained, useful items may include:

  • The complete written report and any amended or supplemental version.
  • The questioned latent image and the exemplar image actually compared, with any available enhancement or processing records.
  • The examiner’s notes or bench records describing the observations, suitability decision, comparisons, and conclusion.
  • The lab procedure in effect at the time, including how it defines its conclusion categories and requires verification.
  • Any AFIS/ABIS search summary, candidate information, later examiner comparison, and verification record.
  • The evidence collection and custody records, plus information about the item’s surface, handling, and access before collection.

The ASB Standard 167 addresses what a written report should identify, including the item and exemplar, examination and conclusion, any database-search summary and limitations, verification, the lab’s conclusion definitions, and the basis for the opinion. It calls for a report to state that the presence of friction-ridge detail on an item does not indicate the print’s significance or time frame of deposition. The standard does not guarantee that every underlying note or record will be produced in every case; counsel can assess the appropriate request and any limits.

For help reviewing the charging papers and the available forensic records, contact the Law Offices of David S. Chesley at (800) 755-5174. The firm’s California violent-crime defense page provides broader criminal-defense information.