New forensic techniques for fingerprint

New forensic techniques for fingerprint detection help crack unsolved crimes

Violent crime, involving guns and knives, is on the increase across the world. While fingerprint evidence is central to solving such crime, recovering usable images is problematic with less than 10% successfully recovered. The University of Leicester is combatting this with new technologies to reveal previously undetectable fingerprints on bullets and knives involved in crimes of violence and on other metallic objects either of intrinsic value (precious or commodity metals) or involved in volume crime (including tools used for burglary).

Conventional technology to visualise fingerprints on spent shell casings has produced poor results because the underlying chemistry requires the sweat deposit left by the finger to remain intact. Additionally, fingerprints are often deliberately removed or damaged by the environment.

Dr John Bond and Professor Robert Hillman from the University’s Department of Chemistry have developed two different technologies to visualise fingerprints on metals after the sweat deposit has been largely lost. One uses microscale corrosion and the other utilises electrochromic polymers:

Microscale corrosion

Fingerprint deposits on metals can, in relatively short periods of time, cause corrosion. This corrosion creates an indelible image of the fingerprint, long after the fingerprint residue is lost. The method identifies microscopic amounts of corrosion and visualises the fingerprint by applying a high voltage to the metal and then adding ceramic beads coated with a fine powder. The beads interact with the corrosion products on the surface, revealing the original fingerprint pattern.

Electrochromic polymer

In this technique, the fingerprint material acts like a mask or stencil, blocking an electric current that is used to deposit a coloured electroactive film. The templating action directs the coloured film to the regions of bare surface between the fingerprint deposits, thereby creating a negative image of the print. Unlike conventional detection methods, the polymers used by the University of Leicester researchers are electrochromic, that is to say they change colour in response to an applied voltage.

These technologies have already had a significant impact, helping police forensic departments worldwide solve recent homicide investigations and re-open cold cases. In 2012, evidence from the corrosion enhancement technique was heard and accepted by the Superior Court of the State of California, setting a precedent in the US legal system.

New forensic products have been developed by commercial partners and are being sold to forensic practitioners worldwide, stimulating the economy. The microscale corrosion technology has been patented and commercialised with UK industrial partner Consolite Forensics. The research helped the company develop a new optical system to recover fingerprints from gun cartridges (CERA LT), offering a rapid and simple to use product with a fully integrated high resolution camera. The company launched the product in the summer of 2013, making its first sale to the Grand Rapids Police Department, Michigan USA. The electrochromic technology has been patented and is being developed in collaboration with the UK Home Office Centre for Applied Science and Technology.

The corrosion and electrochromic polymer technologies have been incorporated in the 2014 UK Home Office Fingermark Visualisation Manual, making them available to police forces across the UK.

Fingerprint Recognition
Fingerprint biometrics is the most popular, widespread, reliable and efficient biometric technology available today. Due to its versatility, fingerprint biometrics is applicable in almost all areas that require clear identification.

Fingerprint Biometrics Features

Fingerprints are distinct to each person thanks to unique papillary features and are different even in twins. Fingerprint patterns remain unchanged throughout the entire adult life and are easily produced for identification.

If a finger is damaged, other fingers that are previously enrolled into the system can also be used for identification.

Processing Fingerprints

Special biometric scanners are used to capture fingerprints. There are three major types of fingerprint scanners: capacitive, sweep and optical.

Capacitive scanners are the most affordable but they are not durable. Since capacitive scanners generate an image of the ridges and valleys that make up a fingerprint using electrical current, such scanners are extremely vulnerable to electrostatic charges. They fail to perform once a person with electrified fingers (wearing wool or silk clothing) touches a scanner. In addition, fingerprint images captured by capacitive scanners are of an extremely poor quality.

The most reliable scanners are optical ones. They are a little more expensive than other biometric devices, but are durable, cost-effective and user-friendly. Fingerprint images taken by an optical scanner are of the highest quality.

Sweep (thermal) scanners are somewhere in between. To capture a fingerprint, a finger is swept over the sensor and is captured in rows, sub-images or slices, forming a biometric template. To be successfully identified with sweep scanners, users have to apply a consistent speed and manner of applying a finger, which is no easy task.

According to the latest research, optical scanners are the best as far as hygiene-related issues are concerned.

NEC has dedicated over three decades in developing the most efficient and accurate fingerprint identification technology. And today, NEC is the world’s leading supplier of fingerprint biometrics for both law enforcement and identity management applications.

NEC fingerprint identification technology is empowered by a unique matching algorithm (i.e., the minutiae and relation method) that uses ridge counts and the relationship between minutiae. This enables us to provide the lowest false accept and false reject rates (FAR and FRR) - with the fastest 1:n database searches for identification.

In addition, Positive Identification (PID) adds another innovative and competitive edge to our fingerprint identification technology. Emerging from NEC’s proven AFIS technology, PID provides the most advanced pattern identification and fingerprint matching available today.
Features
The NEC Difference
Technical Highlights

NIST-Proven Accuracy

Features

NEC's AFIS delivers high-level benefits and offers a variety of advanced features to meet law enforcement identification demands.

Fingerprint and palmprint identification
Positive Identification (PID)
Advanced processing for finger, latent, palm and slap matching
Enhanced Search Sending to Other AFIS
Seamless interface to live scan units, mugshot systems, criminal history systems, etc.

The superiority of NEC matching cannot be overstated. NEC’s AFIS does not just match fingerprints to solve crimes. Unlike our competitor’s systems, the NEC AFIS is not only a tenprint registration system but also a fingerprint repository for the identification of dangerous criminals. Furthermore, the capability that distinguishes NEC’s AFIS technology from that of our competitors is its unsurpassed latent identification accuracy and speed - solving crimes is the number one AFIS priority.

NEC AFIS is the first AFIS that uses ridge counts and relationships between minutiae in its matching algorithm. This algorithm allows AFIS to match distorted prints while maintaining matching selectivity. In addition, NEC’s use of “zone” data reduces the number of false minutiae by ensuring that only minutiae in “clear zone” are used in matching. These features allow NEC AFIS customers to achieve high hit rates while reducing the number of candidates to be compared with.
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Technical Highlights

Minutiae and Related Method

The Minutiae and Related Method is a matching algorithm designed by NEC, which uses ridges and minutiae inside a clear zone of fingerprints to achieve accurate fingerprint identification.

Minutiae and Related Method
A finger minutia is a fingerprint ridge ending, or a ridge bifurcation where the ridge separates into two ridges - the characteristics that make each fingerprint unique. Because the skin at the ends of fingers, where fingerprint patterns are located is soft, the positions and directions of minutiae are subject to great deal of distortion, depending on how the finger is pressed against the surface receiving the print. The number of ridges between minutiae however, never changes. By encoding these ridge-counts together with the minutiae, that is the relation between minutiae, NEC AFIS provides the most positive matching for all types of fingerprints.