Beyond Identification
Written by Kristi Mayo   

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A NEW TECHNOLOGY that is currently under development in the United Kingdom could provide law enforcement with a new way to glean information from latent fingerprints. The technique marries a characteristic of fingerprints that is familiar to most forensic professionals—the sweat secreted from pores in friction ridge skin—with chemicals and particles that are probably less familiar—metabolites, antibodies, and nanoparticles.

Utilizing these components, the scientists working on this technology say fingerprints can reveal more about individuals than their identity. The fingerprints can also reveal information about a person’s lifestyle—for example, whether the individual has been using nicotine or drugs of abuse.

The company pioneering this technique, Intelligent Fingerprinting Ltd., is a spin-out from the University of East Anglia in the United Kingdom. Its founders, Professor David A. Russell and Dr. Sue M. Jickells, co-authored a paper in 2007 that appeared in the chemistry journal Angewandte Chemie International Edition. In the paper, they wrote about a technique that makes it “...possible to obtain direct chemical information from drugs or drug metabolites present in minute quantities of sweat deposited with a latent fingerprint to provide ‘lifestyle intelligence’ regarding an individual.”

Five years later, that research has grown into a company of six individuals working to commercialize the Intelligent Fingerprinting technique, setting their sights on markets such as law enforcement, border security, prison services, and health care. Their efforts have caught the attention of international media outlets in recent months, as well as the interest of the UK government’s Home Office.

How it Works

When a person deposits a fingerprint, he leaves behind secretions from apocrine and eccrine glands. While the substances from the apocrine glands are transferred to fingers from casual contact with the face and hair, the secretions from the eccrine glands (sweat) come directly from pores in the friction ridge skin.

This sweat contains water, chlorides, inorganic ions, lactic acid, ammonia, creatinine, and amino acids. More importantly for this application, the sweat can also contain metabolites—chemicals produced in the body as a result of normal metabolic processes. These can be used to determine what substances have been ingested or otherwise put into a person’s body. Specific metabolites correspond with the substance that has been metabolized. For example, a metabolite of nicotine is cotinine. After a person smokes a cigarette, cotinine can be found in his or her saliva, serum, urine — and sweat.

In order to identify the metabolites present in a fingerprint, Intelligent Fingerprinting utilizes high-sensitivity detection reagents that are made of antibody-coated nanoparticles. These tiny particles (sized between 1 and 100 nanometers) are composed either of gold or iron oxide, and are bound to antibodies using proteins and linker molecules. The antibody nanoparticle conjugates then bind to their targets: metabolite antigens in the fingerprint.

Initial reagents have been devised by Intelligent Fingerprinting for the detection of metabolites of nicotine, drugs of abuse, and the stress hormone cortisol.

Practical Benefits

The detection of drugs and their metabolites in body fluids, including blood, urine, and saliva, are well known, and the process is widely applied in standard drug-testing and toxicology settings. According to Intelligent Fingerprinting, some of the drawbacks to those methods include the need to collect invasive samples, biohazard risks, cross-reactivity with other substances in the samples, and the requirement for cold or frozen sample transport and storage. In addition, tests are sometimes susceptible to contamination, leading to increased levels of false positives, or can be cheated by the person undergoing the testing procedure by swapping another person’s sample for their own.

The scientists at Intelligent Fingerprinting feel they have overcome many of those potential problems by devising a method that allows quick and easy collection and stable storage of the sample (the fingerprint) at room temperature, along with creating a watertight chain of custody. In addition, the method provides the opportunity to not only test for the metabolites, but also to verify the identity of the individual through standard fingerprint comparison techniques.

Products

In its efforts to commercialize its new method, the company developed two products. First, a prototype of a handheld device was released in November 2011 that allows rapid screening of fingerprints directly from the individual, such as in roadside screening.

Second, a line of reagent sample kits has been developed that can be used to analyze samples taken directly from an individual, or for the analysis of latent fingerprints recovered from touched surfaces. Reagents have been developed for the analysis of:

  • Benzoylecgonine (cocaine metabolite);
  • Ethylidine Dimethyl Diphenyl-pyrrolidine (methadone metabolite);
  • Methadone;
  • Morphine (heroin metabolite); and
  • Tetrahydrocannabinol (the main psychoactive substance that is found in cannabis plants).

At the Crime Scene

Using the reagent sample kits, latent prints lifted from a crime scene could be tested for the presence of various metabolites. This would give investigators additional information about an individual, such as whether they have used cocaine or marijuana.

The four-step process detailed by the company follows:

  1. The fingerprint is imaged using white oblique light to create a record for comparison later in the process.
  2. The fingerprint (or the portion that has been reserved for analysis) is treated by an aqueous solution of the nanoparticle antibody conjugates.
  3. This is then incubated for a few minutes to allow the antibodies to bind with the metabolites in the fingerprint.
  4. Finally, the excess antibody conjugates are removed. Although it is possible to view the results of the analysis with white light, the fingerprint is further developed by the second application of a fluorescent dye — also coupled with antibodies — that will bind to the nanoparticles from the first application.

Intelligent Fingerprinting method nanoparticles white light image fluorescence
Figure 1.

A positive result, as shown in Figure 1, will produce an enhanced fingerprint that is of high definition and readily useful for identifying the owner through conventional comparison procedures. An even closer look, as shown in Figure 2, will reveal that the nanoparticles attach to the latent print in the largest concentrations around the individual sweat pores, and then spread out along the ridges to create the image of the fingerprint. This is consistent with the metabolites being excreted from the pores—and shows that the presence of the metabolites is not the result of innocent contamination or secondary transfer of another person’s metabolites.

Intelligent Fingerprinting nanoparticles antigens metaboliteIntelligent Fingerprinting nanoparticles antigens metabolite
Figures 2 & 3

As Intelligent Fingerprinting works on validating this technology, a few questions remain to be answered. First, little work has been done to determine whether this technique can be applied to latent prints that have been developed using another enhancement technique, such as dusting with fingerprint powder or superglue fuming. According to Dr. Paul Yates, the business development manager for the company, the technique so far has only been proven on prints in situ or collected with lifting tape.

“We will be looking at how the technique can be used with different fingerprint-enhancement techniques that are around at the moment,” said Yates. “For sure, right now, we don’t know if it will work with all of the techniques. But we know that the theory works that if you can lift the metabolites with the print, we are still able to use our technique… as long as you haven’t used a chemical technique that might interfere with the metabolites.”

Yates indicated that further work planned in coordination with the UK government’s Home Office will deal with testing the combination of the Intelligent Fingerprinting method with other chemical enhancement techniques.

Another question that remains to be answered is how a technician could test for a range of different metabolites on a single latent print. As the technology currently exists, each reagent tests for just one specific metabolite.

“You would need to test prints for specific metabolites,” said Yates. “For example, if you were testing for drugs of abuse, you would either test a single fingerprint with a cocktail of different nanoparticles, each tagged with different antibodies… or you would subdivide the print into sections and test different parts with different reagents. Either is possible; at the moment, we are just trying to work out what is the most effective way.”

Finally, there are questions about just how far this technology could go—and what kinds of possibilities it could offer to crime scene investigators. The company has already determined that the stress hormone cortisol can be detected using the antibody nanoparticle conjugates. Could other hormones be detected, as well—such as hormones that would help establish the sex of the person who left the print?

“Nobody has looked at fingerprint sweat and made a definitive map of what is in there,” said Yates.

“What we know is that within a certain mass range, you will get metabolite chemicals in the fingerprint. And that mass range will encompass a number of different hormones. But, we don’t know until we look.”

For More Information

Intelligent Fingerprinting currently estimates that their first products will be available some time in 2013. To learn more about the technology being developed by the company, go to their website: www.intelligentfingerprinting.com

About the Author

This e-mail address is being protected from spam bots, you need JavaScript enabled to view it is editor of Evidence Technology Magazine.

 
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