Advances in Fingerprint Technology
Kristen Cohen, M.Ed., NCSTL Administrative Assistant
Since 1880, when Dr. Henry Faulds first published his paper on using fingerprints for identification purposes and recording them using printing ink1, fingerprinting technology for the purpose of crime investigation has surpassed early twentieth-century law enforcement expectations. Currently, at the start of the twenty-first century, the technology utilized in the collection, identification, and storage of fingerprint technology for crime investigation has made great strides in the last five years.
Recent advances in fingerprint collection devices and techniques expedite crime scene investigations. Some advances are simple, such as the situation where a man selling stolen watches sent mobile phone images of his merchandise, yet inadvertently captured portions of his hands in those same images. Those portions of his hands revealed enough detail so as to allow police to identify him.2 Other recent methods of fingerprint collection prove much more advanced than electronically recorded images of prints. Digital holography, micro-X-ray fluorescence (MXRF), and the scanning Kelvin Probe (SKP) employ recent scientific and technological advances to obtain latent fingerprints without compromising or destroying the actual fingerprint evidence found at a crime scene.
Digital holography captures the image of the print, analyzes it, and then reconstructs it three-dimensionally. The highly technical procedure “…is a new imaging technology which combines the advantages of both the optical holography and digital processing. Both the theoretical analysis and the experimental results showed that digital holography does not destroy the on-site fingerprints, overcomes the shortcomings of traditional fingerprint acquisition methods, and as a simple and effective acquisition method can be applied to the criminal investigation field.”3 This method records and reconstructs the structure of latent fingerprints using a Digital Interference Holography scanner.4
Micro-X-ray fluorescence, also known as MXRF, utilizes x-ray beams to detect elements, such as those found in human sweat, to form the image of a fingerprint. After exposure to the x-ray beam, these elements become detectable and form the fingerprint image that might otherwise have been missed or compromised using previous fingerprint detection methods, such as powders or liquids. The MXRF also proves useful with acquiring children’s fingerprints which are usually difficult to detect because of the absence of the oily substance called sebum that adheres the traditional fingerprinting enhancers to it.5 In addition, other detectable substances become useful in real-life crime scene investigation, such as saliva and sunscreen. Since MXRF does not require physical contact with the surface, it establishes an advantage over traditional methods of fingerprint collection; however, it suffers from another problem inherent in its own fundamental process. Some studies using MXRF technology detect prints from one subject with no problem, while the prints of another subject remain undetectable, leading researchers to conclude that diet and/or individual elemental composition can affect MXRF fingerprint acquisition.6 Such a problem suggests that the MXRF technique may be a better choice as an additional fingerprint acquisition method rather than the primary one for crime scene investigation.
Another advanced fingerprint acquisition technique utilizes the scanning Kelvin Probe (SKP). This method “measures the voltage, or electrical potential, at pre-set intervals over the surface of an object on which a fingerprint may have been deposited. These measurements can then be mapped to produce an image of the fingerprint. A higher resolution image can be obtained by increasing the number of points sampled, but at the expense of the time taken for the process. A sampling frequency of 20 points per mm is high enough to visualize a fingerprint in sufficient detail for identification purposes and produces a voltage map in 2-3 hours.”7 The SKP also resolves a previous problem with traditional fingerprinting techniques: the choice between preserving fingerprints themselves as evidence or sampling the material in the fingerprint for DNA analysis evidence. Since the SKP preserves the fingerprint in its original state, both tests can be employed, greatly adding to the evidence cache.8
The SKP proves helpful in obtaining fingerprints from warped non-planar surfaces as well, including fired cartridge cases. The evolution of criminal techniques and terrorism require that crime scene investigation and detection methods evolve as well. With that in mind, “the very latest research…has found that physically removing a fingerprint from a metal surface, e.g. by rubbing with a tissue, does not necessarily result in the loss of all fingerprint information.”8 The reaction between the inorganic salts contained in the fingerprint and the metal surface begin to occur from the moment of contact, and the resulting metal-ion complexes are not easily removed.9 The SKP permits such fingerprint detection and provides a valuable tool for a previously illusive forensic challenge.
Identification and Storage
With cutting-edge fingerprint collection techniques, the identification and storage of these fingerprints represent crucial and fundamental elements to the crime-solving process. The Federal Bureau of Investigation (FBI) claims to house the fingerprints and criminal histories of sixty-six million people along with twenty-five million “civil” fingerprints.10 Until this year, these prints and records were held in the Integrated Automated Fingerprint Identification System (IAFIS). In March, 2011, the FBI announced their move from IAFIS to a new technology platform called the Next Generation Identification (NGI) System. The NGI System adds several new biometric features and expects to significantly reduce processing times compared to the previously used IAFIS. While the IAFIS took two hours on average to identify fingerprints, the NGI System will be capable of doing the same job in ten minutes.11 “The NGI System will automate quality checks that in the past were done manually, and include better search functionality and improved processing of latent prints, improved storage of palm prints, as well as better integration of photos with fingerprint and arrest data.”12 In the future, “…the NGI System will be built out to include ‘multimodal’ biometric data, such as retina scans, scars, tattoos and facial recognition.”13
1 Faulds, Henry (28 October 1880). “On the skin-furrows of the hand” ()http://www.galton.org/fingerprints/faulds-1880-nature-furrows.pdf Last checked on July 1, 2011.
2 Manchester Evening News, Thursday 17 June 2010, front page ()http://en.wikipedia.org/wiki/Fingerprint.
3 Ting Luo Dayong Wang Yunxin Wang Huakun Cui Yizhuo Zhang, “Fingerprint Acquisition for the Criminal Investigation by Digital Holography,” 2011 International Conference on Information Science and Technology (ICIST), 26-28 March 2011. Found at http://ieeexplore.ieee.org/search/freesearchresult.jsp?newsearch=true&queryText=fingerprint+acquisition+for+the+criminal+investigation+by+digital+holography (last checked July 1, 2011).
4 Mariana C. Potcoava and Myung K. Kim, "Fingerprint scanner using digital interference holography", Proc. SPIE 7306, 730627 (2009); doi:10.1117/12.818276 . Found at http://dx.doi.org/10.1117/12.818276 (last checked July 1, 2011).
5 Montaldo, Charles, “New Fingerprint Detection Technology Developed,” 2006. Found at http://crime.about.com/od/fingerprintevidence/a/micro_x.htm (last checked July 5, 2011).
6 Worley, Christopher G. “Detection of Visible and Latent Fingerprints by Micro-X-ray Fluorescence,” Powder Diffraction, Volume 21, Issue 2, 2006. Found at http://www.aip.org/dbis/stories/2006/15248.html (last checked July 5, 2011).
7 Swansea University College of Engineering, “Forensic Fingerprint Detection.” Found at http://www.swansea.ac.uk/engineering/materials/research/corrosionandcoatings/forensicfingerprint (last checked July 5, 2011).
10 “FBI Unveils Faster Fingerprint ID Technology,” Government Technology: Solutions for State and Local Government, March 8, 2011. Found at http://www.govtech.com/public-safety/FBI-Unveils-Faster-Fingerprint-ID-Technology.html (last checked July 5, 2011).