Fingerprints

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Note: This article is mainly based on a document entitled "Fingerprints" by the non-governmental organization "Forensic Experts and Jurists' Association"[1].

Definition

The surface of the human skin on the tips of the fingers, palms of the hands and soles of the feet, unlike the skin on most of the rest of the human body, is continuously corrugated with narrow ridges.

Fingerprint is an impression of the friction ridges of all or any part of the finger. In a wider use of the term, fingerprints are the traces of an impression from the friction ridges of any part of a human or other primate hand[2].

Why are fingerprints utilized?

Fingerprints (and other ‘friction skin’ patterns) are used as a means of identifying people, particularly in criminal justice systems worldwide. Fingerprint evidence has enjoyed widespread acceptance and use as a legal means of proving in the courts for many years.

This type of evidence plays a crucial role in criminal investigations, and the fingerprint examination (expertise) is the most applied investigative means in criminal matters.

A person’s fingerprints are unique and do not change during the course of their life. No two fingerprints have ever been found alike in many billions of comparisons. That’s why fingerprints can be used to quickly and efficiently confirm (or disprove) a person’s identity.

Fingermarks can be collected at a crime scene and have the potential to link a series of crimes together, or to place a suspect at the scene. Fingerprints play an equally important role in indentifying victims following a disaster such as a cyclone, earthquake, bombing or other attack[3].

When are fingerprints utilized?

Fingerprint identification is utilized at many levels of the process. Fingerprints are commonly used in relation to:

  • Warrants and extradition: police officers and jailors use such identification to confirm a suspect's identity and to facilitate arrest.
  • Charging decisions: Positive and negative conclusions on fingerprint identification evidence determine the strength of the case and the appropriate charges to file
  • Jury Trials: Latent fingerprint examiners, which are the prosecution's expert evidence also use this type of evidence to conclude whether the fingerprints of the accused match those found at the crime scene.
  • Appeals level: fingerprint identification evidence is used to bolster the prosecution's argument that the jury's verdict was appropriate and that any other alleged error at trial should be viewed as harmless error considering the strong weight of the fingerprint identification evidence.

Types of Fingerprints

There are two types of fingerprints:

  • Rolled or inked prints: obtained by individuals inking their fingers and rolling each fingertip from edge to edge on paper - these are also called known fingerprints because the identity of the person is known when they are taken and
  • Latent fingerprints: obtained by using fingerprint powder to make the latent print visible. Once the latent print is made visible, tape is used to lift the latent print from its original surface onto a lift card. These lift cards are examined by fingerprint identification experts who compare the friction ridge detail in the known print. Both types are utilized in the criminal justice system.

Methodology: ACE-V

Fingerprint examiners carry out a visual comparison of a crime scene mark (fingermark) and prints from a known individual (fingerprint). These sources are both impressions that are used in comparison process realized by the fingerprint specialists. A mark left on a surface is generally being compared with a print taken in controlled conditions for example using ink or, in current practice, ‘Livescan’, an optical device used to capture impressions digitally.

The comparison process is to determine whether a mark and a print match so that the mark can be ‘individualised’. By the mark being ‘individualised’ fingerprint examiners mean that it can be attributed to the known individual to the highest level of specificity: it is unique to that one individual out of the whole human population.

Most examiners use the comparison methodology that is called “ACE-V”.

ACE-V is an acronym of words that refers to the sequence of working scientific method whereby:

1. An examiner analyses a mark. The purpose of the analysis is to assess the quantity, quality and specificity of the present fingermark. In this stage, expert tries to assess the evidentiary value of the fingermark (i.e., its intrinsic value for discriminating a unique source).

2. Having done so the examiner compares the mark to a known print. If the mark determined to posses sufficient value, and the known exemplar is also sufficient for comparison purposes the expert proceeds the comparison phase. The comparison is the side by side comparison of the images. Features present in one image should be found in the other one, in the same relative position, orientation and number of intervening ridges.

3. Having compared the images the examiner evaluates what he or she has seen and reaches a decision. After the side by side comparison is complete the expert must formulate an opinion about the sources of the images. The decision making process is the stage of evaluation, where one of three general categorical conclusions is possible: individualization (identification), exclusion and inconclusive opinion.

4. The results of the evaluation stage are then subject to verification by one (or more) additional examiner(s). Finally, a review of the conclusion by another examiner or examiners, using the ACE process, provides a cross-check to ensure that the decision is not based on a marginal subjective judgment of one individual but enjoys acceptance as the consensus conclusion of a number of examiners. This check is a quality assurance mechanism and is the final phase of the ACE-V[4].

Standards for Identification

The law enforcement agencies or forensic laboratories of different countries apply various standards (criteria) for identification in fingerprint examination. At present, there are two well-known standards: (a) the empirical approach (also called “minutiae threshold” or “numerical standard”) (b) the holistic approaches (also called “non-numerical approach”).

The empirical approach calls upon the examiner to require a minimum number of minutiae (or points) in the agreement (without discrepancies) between a mark and a print before concluding on individualization. The number of points required varies from country to country and also from examiner to examiner in the same country. There are, e.g., 16-17, 8-12, 10-12 or 12-point rules that various country use in fingerprint examinations depending on the standard that the law enforcement or expert agency of a certain country has adopted[5].

The holistic approach calls for an assessment by the examiner of each comparison based on its own merit (in terms of quality and quantity as revealed by the mark and the print). The expert concludes on an individualization when he/she is satisfied that there is “sufficient” correspondence (or sufficient discordance in the case of an exclusion) between the compared images. This informed judgment is based on training, experience, and expert knowledge[6].

Points of Match

Fingerprint experts reach a conclusion as to whether the fingerprints found at the crime scene match those of the accused on the basis of matching points'. At the moment there are no universal standards of matching points. Examiners historically have employed identification standards ranging from eight to sixteen matching characteristics, or "points of similarity." Yet, the FBI has stated that there should be no minimum standard and that the determination of whether there is a sufficient basis for an identification should be left to the subjective judgment of the individual examiner. The same is applied in the United Kingdom. On the contrary, other countries have set standards. For example, Australia has a minimum standard of twelve matching ridge characteristics whereas France and Italy have sixteen.

Legal regulations

The procedure of appointment fingerprint examination and fingerprint expert’s involvement mechanism in criminal process depend on the peculiarities of criminal justice system. There is a strong difference between adversarial and accusatorial (inquisitorial) systems in respect with the involvement of an expert in criminal proceedings.

At adversarial systems, it is common for (fingerprint) experts to be called by both parties: the prosecution and the defence. For this character in adversarial systems, experts are called ‘party selected experts’. The Court’s role in appointment of an expert in adversarial justice is essentially restricted.

By contrast, in inquisitorial systems experts are appointed by the law enforcement officials (as well as examining/investigative judge) and the court (trial judge), and not by the defence lawyers[7]. The experts in inquisitorial criminal justice are called ‘court appointed experts’ or ‘official experts’.

This difference is related to the aim of justice regarding which an essential difference between adversarial and inquisitorial systems exists: the first type of system seems to deny the existence of an ‘absolute truth’, whereas inquisitorial systems take the presumption of an ‘absolute truth’ as a starting point when engaging expert evidence[8]. The aim of participation of an expert in trial at common law is to win in ‘battle of experts’, albeit in inquisitorial trial at continental law, expert is entitled to assist the court in finding the truth and not the winning the case by a party.

However, in inquisitorial procedure, the parties are not completely out from the expert reporting process, since it is sometimes possible for them to request that certain specific questions be put to the expert, to make comments on the expert's report once it has been placed in the case-file, to raise supplementary questions and possibly request the appointment of an expert to give a second opinion, to request the expert at the hearing to clarify material which is still unclear, and to have their own private expert interviewed[9].

Legal challenges

There are also certain legal challenges that exist in fingerprint examination in practice. Here we are stressing some legal challenges that are more important in our view and are under debate in professional literature.

  • The first legal challenge is the admissibility of fingerprint evidence. (Of course, this challenge is common for other scientific (forensic) evidence as well, that we will discuss in our next presentations). This challenge refers to especially those legal systems which have legally adopted scientific admissibility requirements for expert evidence.

For instance, in adversarial systems, especially in the United States, the institute of scientific admissibility of expert evidence exists, that contains number of rules as admissibility criteria of expert evidence from the view of its scientific reliability. These requirements are defined firstly by the Rule 702 of the Federal Rules of Evidence 1975 of the United States. According to this Rule (‘Testimony by Experts’), “If scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education, may testify thereto in the form of an opinion or otherwise, if (1) the testimony is based upon sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case”. Rule 702 is a result of several well-known cases in USA[10] that are special guidelines to help the judge to assess scientific reliability and probative value of expert evidence[11].

In inquisitorial criminal justice, the court, in assessing the evidence, is not bound by formal rules. An exception to this principle is the exclusionary general rule: judges may not base their conviction on unlawfully obtained evidence.

  • The second legal challenge that we prefer to stress here is the legal regulation of fingerprint examination method. In particular, some authors find the necessity to regulate the fingerprint examination methodology by law. The core sense of this approach is that fingerprint evidence obtained by a method, that is not legally regulated, cannot be considered as a legally obtained evidence and ‘…the defence may argue that evidence obtained with the help of this (forensic) method is “illegally obtained evidence”. Art. 6 of the ECHR guarantees every defendant a fair trial. Use of illegally obtained evidence may very well conflict with the principle.’[12]. Thus, the utilization of methods that have no legal basis might very well be in conflict with the fair trial concept laid down in Article 6 of the ECHR.
  • If the method or technique furthermore invades the privacy of the defendant, the defence can also argue that Art. 8 (the right of privacy) has been violated if the method used was not “in accordance with the law”.’[13]. The application of certain expert methods is related to human rights and fundamental freedoms. Especially, the methods that are directly addressed to individual identification (e.g., fingerprints, DNA analysis, handwriting, audio-video records, etc.) make it possible to receive amount of personal information[14]. These methods restrict the right of privacy and, therefore, bear potential for its prejudice. Hence, the application of these methods should be realized only in the borders of applicable procedural guarantees.

Notes

  1. FEJA Website: www.feja.am
  2. See Fingerprint, http://en.wikipedia.org/wiki/Fingerprint
  3. See Interpol, Fingerprints, www.interpol.int/content/.../14/.../Factsheets_EN_feb2012_FS03.pdf
  4. See The Fingerprint Inquiry Report. Scotland. Published on Behalf of The Fingerprint Inquiry by APS Group Scotland. Vol. 1, 2011, Ch 36; Jamieson Allan, Moenssens Andre (eds. in chief) Wiley Encyclopedia of Forensic Science. Chichester: Wiley, 2009, Vol. 3, pp. 1286-1287.
  5. See, e.g., Nijboer J.F., Sprangers W.J.J.M. (eds.) Harmonisation in Forensic Expertise: An Inquiry into the Desirability of and Opportunities for International Standards. Amsterdam: Thela Thesis, 2000, p. 289
  6. See, e.g., Joseph Polski, Ron Smith, Robert Garrett, et al. The Report of the International Association for Identification, Standardization II Committee, 2010, pp. 28-29
  7. See Malsch M., Freckelton I., The Evaluation of Evidence: Differences Between Legal Systems, ‘Legal Evidence and Proof: Statistics, Stories, Logic’, Edited by Kaptein Hendrik, Prakken Henry, Verheij Bart, Cornwall, 2008, pp. 124-125
  8. See supra note, p. 131
  9. See Champod Ch., Vuille J., Scientific Evidence in Europe – Admissibility, Appraisal and Equality of Arms, Comparative Study on Scientific Evidence Drawn up for the Bureau of the Council of Europe’s, European Committee on Crime Problems (CDPC), Report on 59th Plenary Session, Appendix VI, Strasbourg, 7-10 June 2010, p. 90
  10. Frye v. United States 293 F 1013 (D.C. Cir. 1923); Daubert v. Merrell Dow Pharmaceuticals Inc., 113 S. Ct. 2786 (1993); General Electric Co. v. Joiner 522 U.S. 136 (1997); Kumho Tire Co. v. Carmichael, 526 U.S. 137 (1999)
  11. See also Jamieson Allan, Moenssens Andre (eds.-in chief) Wiley Encyclopedia of Forensic Science. Chichester: Wiley, 2009, Vol. 3, p. 1289
  12. Nijboer J.F., Sprangers W.J.J.M. (eds.) Harmonisation in Forensic Expertise: An Inquiry into the Desirability of and Opportunities for International Standards. Amsterdam: Thela Thesis, 2000, p. 174
  13. See Ibid.
  14. See Kastanidou-Symeonidou, E., “DNA Analysis and Criminal Proceedings: the European Institutional Framework”, European Journal of Crime, Criminal Law and Criminal Justice, 2011, Vol. 19, pp. 139-160

See Evidence