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Fingermark Individualisation

Fingermarks are widely used as forensic evidence. When a fingermark from a crime scene is matched with a fingerprint of a suspect, the match is universally accepted as highly probative evidence. For many years categorical conclusions were considered mandatory for reporting fingerprint evidence. Traditionally this is an all-or-nothing approach where identifications were reported only when fingerprint examiners could find sufficient matching characteristics. As a result, many low quality fingermarks that failed to meet this standard were considered to have no associative value at all. As a consequence, fingermarks with minimal dactyloscopic information were often left out of the forensic investigation and were being discarded.

The Netherlands Forensic Institute (NFI) applies a probabilistic approach for fingermark comparisons since 2011. This approach allows for reporting the evidential strength of low-quality fingermarks.

Image: ©Netherlands Forensic Institute / Netherlands Forensic Institute
Fingermark investigation on a knife

What is the probabilistic approach?

The NFI uses a Bayesian framework for the evaluation of forensic evidence. Fingerprint examiners express the likelihood ratio of their observations, using two mutually exclusive hypotheses. This likelihood ratio is expressed verbally using a verbal probability scale [1].

To support their findings, the NFI has developed an encoded dataset containing multiple levels of dactyloscopic information. Through research into the rarity of fingerprint features NFI fingerprint examiners are able to report a frequency of occurrence of dactyloscopic information in case of a match [2], [3].

With the probabilistic method, previously discarded marks can now make a useful, quantifiable contribution to the forensic case. The results can be used in court as corroborating evidence.

[1] https://www.forensischinstituut.nl/publicaties/publicaties/2017/10/18/vakbijlage-waarschijnlijkheidstermen

[2] A. De Jongh, A.R. Lubach, S.L. Lie Kwie, I. Alberink, Measuring the rarity of Fingerprint Patterns in the Dutch Population Using an Extended Classification Set, J. Forensic sci, 64 (1) (2018) 108-119.

[3] De Jongh A, Lubach AR, Lie Kwie S, Loadsman-Wammes FDLV, Alberink I. Measuring the rarity of core-delta distances in fingerprint patterns in the Dutch population. J Forensic Sci. 2024;69(1):94-116.

For which types of cases?

The NFI is one of the few laboratories in the world currently applying a validated and accredited approach for low quality and partial fingermarks. The method can be used in the following circumstances:

  • Regular forensic case investigations: containing a fingermark  that does not meet the sufficiency standard for individualisation.
  • Cold-case investigations: re-examining dactyloscopic trace material.  
  • Second opinion: re-examining dactyloscopic trace material, in the context of providing a second opinion.

For more information, please contact our Account Management Team.