In a joint project, researchers have developed a "Forensic Hyperspectral Imager" device based on hyperspectral imaging techniques, which can differentiate layered fingerprints into individual prints and detect untreated latent fingerprints from surfaces such as walls and magnetic sides of railway tickets.
In collaboration with JFE Techno Research Corporation and the National Research Institute of Police Science, Professor Sota Takayuki (School of Advanced Science and Engineering) has developed a "Forensic Hyperspectral Imager" device based on hyperspectral imaging techniques, which can differentiate layered fingerprints into individual prints and detect untreated latent fingerprints from surfaces such as walls and magnetic sides of railway tickets.
The device is compact enough to store in a suitcase and is capable of detecting signals from fats and amino acids in fingerprints or fluids noninvasively and without physical contact. Even with the advancement of DNA profiling technology, the uniqueness and permanence of fingerprints make them useful in forensic criminology. With its superior identification methods, the device will improve the abilities of forensic teams and contribute to a safer society by enabling users to promptly identify and arrest suspects. It is also expected that with improvements, this device will be capable of quickly and precisely identifying victims of natural disasters by their fingerprints. The device can potentially open the door to identifying when latent fingerprints are impressed based on their fluorescent spectra. Reliability demonstration tests of the device began with the full cooperation of National Research Institute of Police Science since October 2014.
A revolutionary "Forensic Hyperspectral Imager"
Since the establishment of the lay judge system, it has been becoming increasingly important to present criminal evidence invisible to the naked eye in easy-to-understand images in court. Even with the advancement of DNA profiling technology, the uniqueness and permanence of fingerprints is a valuable forensic asset in identifying suspects. The weakness of current methods (powder, liquid, gas, etc.) is their inability to identify and differentiate accumulated fingerprints and handprints from objects such as magnetic surfaces of railway tickets and photo paper.
2) Research Purpose
The purpose of this research is to develop a compact spectroscopic imaging device based on hyperspectral imaging techniques, capable of detecting human by-products such as fats, amino acids in latent fingerprints and liquids noninvasively and without physical contact.
3) New Methods
The hyperspectral imaging technique (HIT) which was originally developed as a remote sensing technique for observing Earth from space was utilized to develop the device. The technique makes it possible to accumulate within a short time a huge data cube, or hyperspectral data (HSD), that includes two-dimensional positional information and spectral information. Spectral information refers to information such as absorption spectra, fluorescence spectra from human by-products. Configuring HIT and a distance measurement device which measures the distance to an object enables the creation of a fingerprint image comparable with that of the fingerprint database that Japan boasts to the world.
4) Research Results and Findings
Pictured below in image 1 is the compact and portable Forensic Hyperspectral Imager used to detect visible wavelengths. In a laboratory demonstration at the National Research Institute of Police Science, a configuration of the high-power green laser and the device attached with an orange color filter demonstrated detection abilities superior to those of current fingerprint detection methods. Pictured in image 2 are images of (a) a latent palm print on a wall and (b) a fingerprint on the magnetic side of a railway ticket, both of which were invisible by the naked eye but first brought into view by fluorescent HSD obtained under the green laser excitation. By utilizing the fluorescent HSD, it is possible to precisely separate double layered fingerprints into distinct fingerprints at a high success rate (70% at the present stage). An example of the process can be seen in image 3. (a) is a color image taken by an ordinary single-lens reflex CCD camera, (b) is a reconstructed image based on the fluorescent HSD and (c) and (d) are, respectively, the palm print and fingerprint separated through the use of the fluorescent HSD. The green (red) spectrum in (e) indicates a typical fluorescent spectrum of the part of the fingerprint (palm print) displayed by the green (red) box in (b). The palm print was very old and its date of impression could not be identified. However, it was understood that a new fingerprint was impressed on top of the old palm print. The man-machine interface of the device enables users to easily operate it and examine necessary information included in HSD.
5) Research and social significance
This is a revolutionary fingerprint detection device that can not only identify and detect latent fingerprints noninvasively and without physical contact but can also separate layered fingerprints through spectroscopy into distinct prints. It surpasses current fingerprint detection methods in some regards and therefore, utilizing the device in conjunction with current methods is expected to have a tremendous impact in identifying individuals and criminal suspects. Consequently, by preventing and deterring crime, this device is expected to help bring about a safer society and with improvements, is expected to provide an invaluable method for quickly identifying victims of natural disasters. The configuration of a secure transmission system and the device can enable users to instantaneously cross-check data against a comprehensive database and if this method is realized, we will see a drastic decrease in the amount of time it takes to identify individuals.
6) Research going forward
We received feedback from members of prefectural crime labs regarding the portability and usability of the Forensic Hyperspectral Imager pictured in Image 1. Joint tests are currently being conducted with the National Institute Research of Police Science to improve the device's functionality and usability.
Fluorescent HSD suggests that fluorescent spectra of fingerprints change over time. This leads us to believe that in principle, we should be able to identify the time period of a fingerprint's impression based on fluorescent spectra. We believe this is worth investigating. It is important to note that we developed simultaneously a Forensic Hyperspectral Imager usable for near-infrared wavelengths. The devices cannot be used when background noises disrupt signals. In this situation, a time-resolved fluorescent spectral imaging device and/or a coherent anti-Stokes Raman spectral imaging device should be used to detect untreated latent fingerprints. It is possible to use the former device to distinguish signals from latent fingerprint from background noises/signals and the coherent signals used in the latter device are essentially background free. Both of these devices were developed at the National Research Institute of Police Science (JFE Techno Research Corporation). New challenges will be constructing a unique system consisting of three devices each of which plays a complementary role in identifying and detecting latent fingerprints noninvasively and without physical contact.
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