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False Negative

What is a false negative?

A false negative occurs when a system fails to identify something that is known to be present. In simpler terms, the correct answer is “yes,” but the system returns “no.” The known correct answer is called the ground truth.
In fraud detection, a false negative means that a fraudulent document, identity, or activity passes without being flagged. A legitimate customer incorrectly flagged as fraudulent is a false positive.
Biometric matching uses more specific terminology. When two face samples belong to the same person but the system returns a non-match, the error is called a false non-match. Because the meaning depends on the check being performed, reports should state the specific error and metric instead of using “false negative” on its own.

What does a false negative mean in identity verification?

Identity verification systems perform several separate checks:
  • 1:1 biometric comparison. A comparison between samples from the same person that incorrectly returns a non-match is called a false non-match. False non-match rate (FNMR) measures how often genuine comparisons produce this error. The opposite error is a false match, in which samples from different people incorrectly match.
  • 1 biometric identification. A false negative identification occurs when a search fails to return the enrolled person as a candidate above the selected threshold. False negative identification rate (FNIR) measures this error.
  • Presentation attack detection (PAD). A missed attack may be described generally as a false negative, although PAD standards use specific metrics for attacks accepted as bona fide presentations and genuine presentations classified as attacks.
  • Sanctions or watchlist screening. A false negative occurs when the system fails to return a genuine match to a listed person or entity.
Note: industry wording is not always precise.
Vendors and teams may use “false negative” without naming whether the target was fraud, a genuine biometric match, or a watchlist hit. These errors should not be combined into one rate.
Reports should state the check, positive class, ground-truth method, threshold, and test population. The same definitions must be used when comparing vendors.

What causes false negatives?

False negatives can come from poor input quality, weak or outdated references, missing data, unsuitable thresholds, and cases that differ from the system’s test data. Lighting, pose, blur, occlusion, and reference quality may lower a face-match score for a genuine pair.
Document fraud checks may miss a forgery when the image does not show the relevant security feature clearly. Screening may miss a listed person because of aliases, transliteration, incomplete records, or restrictive matching rules.

Why are false negatives important?

A false negative in fraud detection can allow a fraudulent identity, forged document, or prohibited customer to pass.
A false non-match affects a genuine user instead, possibly leading to another capture, manual review, or abandonment.
Separate metrics show whether the problem lies in fraud detection, biometric accuracy, or another part of the verification process.

How can Regula support false-negative analysis?

Regula Face SDK returns similarity scores for 1:1 face comparisons and assesses face-image quality. Active and passive liveness checks provide separate results for presentation attack detection.
Regula Document Reader SDK verifies identity documents using more than 16,500 document templates from 254 countries and territories. It checks document security features and compares information from the visual inspection zone, machine-readable zone (MRZ), barcodes, and supported NFC/RFID chips.
Organizations remain responsible for defining the ground truth, selecting thresholds, measuring each error separately, and setting rules for another attempt or manual review.

FAQ

Is a legitimate customer flagged as fraud a false negative?

No. In a system that treats fraud as the positive class, flagging a legitimate customer as fraudulent is a false positive. A false negative occurs when the system fails to flag genuine fraud. If a face matcher fails to match a legitimate customer with their own reference image, the specific biometric term is false non-match. The errors come from different checks and require different metrics.

 

How is the false-negative rate calculated?

The false-negative rate is the number of false negatives divided by all ground-truth positive cases: False-negative rate = false negatives ÷ (true positives + false negatives). If fraud is the positive class, the denominator contains all confirmed fraudulent cases in the test set. Biometric comparison and identification use specific metrics such as FNMR and FNIR.

 

Is every failed identity verification a false negative?

No. A legitimate applicant may fail because the image could not be captured, a required document was missing, a business rule stopped the process, or a biometric comparison returned a false non-match. Only the last example is a biometric comparison error. End-to-end rejection rates and component error rates should be reported separately.

Does changing the threshold reduce false negatives?

It can, although the effect depends on how the score is defined. For face similarity scores, lowering the match threshold generally reduces false non-matches and increases false matches. Fraud systems may assign scores in the opposite direction, so teams should confirm what higher and lower scores mean before changing a threshold.

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