When discussing nanotechnology, the first aspect often talked about is the technology. But once this topic has been exhausted, the conversation turns to the commercial aspects or potential issues around health, safety and the environment. The discussion does not often moves onto other societal or community issues. This may not be surprising as the applications for nanotechnology that directly focus on these issues do not get a high profile. However, there are a few, and one where there has been a rapid growth in activity in recent years is that of forensics.

In the past few years, television programs such as CSI and NCIS have shown that forensics is a highly technical and skilled profession. The advances in forensic technology have principally been driven by progress in analytical techniques. DNA analysis is the most well known area, although improvements in detection levels of more conventional analysis techniques have also been a factor. However, nanotechnology is promising to have a major impact with the latest developments in the identification of latent fingerprints. Latent fingerprints are deposits left by a combination of excretions from the sweat and sebaceous glands in the skin. They are invisible and require the use of optical techniques or, more commonly, development agents such as powders to reveal the print. Anyone familiar with CSI will have seen the investigators dusting for fingerprints using conventional powders and brushes.

The uniqueness of fingerprints to identify individuals had been suspected a long time ago. Fingerprints have been found in ancient China and on Babylonian clay tablets used for recording business transactions. In 14thcentury Persia, government papers had fingerprint impressions and a doctor suggested that no two fingerprints were the same. Fingerprints are one of only two human characteristics that are unique to an individual, the other being DNA. However it was not until 1902 that fingerprints were successfully used in a criminal trial.

Materials such as carbon black and aluminium flake have been used as latent fingerprint developers for many years as it was found that they worked well under particular circumstances, but there has been minimal activity in developing engineered materials specifically designed for fingerprint development. The ideal fingerprint powder will stick to the residues left by the finger, which give rise to the characteristic patterns that everyone identifies as a fingerprint, but not stick to anything else. Many common materials also stick to the background, making a clear identification significantly harder to achieve. Nanotechnology is being used to engineer particles to overcome this problem.

The first aspect that is being investigated is the use of nanoscale powders to provide clearer images. A number of groups are looking into this, but a group at Sydney University recently reported that 20 nm ZnO powders not only gave better prints and were inherently UV fluorescent but also worked in wet conditions. Something conventional micron sized powders cannot do. Other researchers have been using CdSe particles that are less than 10 nm, which also fluoresce under UV light, to improve the development of fingerprints.

ROAR Particles have looked at extending the use of fingerprints beyond purely improving the definition of the fingerprints. They have been developing nanopowders that have been engineered to enable them to be used in conjunction with SALDI-TOF2-MS. This means that when a fingerprint is developed using these powders, the chemicals, both the residues from contact with other materials and excreted, that form part of the fingerprint, can be analyzed and identified. For example, if the donor of the print has been handling explosives or illegal drugs, then the contact residues will appear in the fingerprint and can be identified. This is only possible with these nano-engineered powders. Since the sweat and other secretions are also a means of removing waste chemicals from the body, the analysis can be taken a stage further and the excreted metabolites can also be identified. So for example the drug users can be differentiated from those who have only handled the drugs.

Another innovation relates to assisting in solving gun crime. Researchers at Leicester University have developed a technique utilising the fact that when someone leaves a fingerprint on a bullet casing, the chemicals in the print start to corrode the surface of the metal. Using a nanoscale developer and an X-Ray source it is possible to image the etched fingerprints even if the casing has been wiped or washed. This opens up the possibility of examining evidence from gun crimes that would not have been possible a few years ago. Something the FBI started to do on a number of high profile cases.

These nanotechnology based techniques are beginning to be evaluated and used by police forces and other law enforcement agencies. It is due to the nanoscale properties of the materials that the new techniques are able to provide either improved performance over existing materials or enable information to be gleaned from a crime scene that would not otherwise have been possible. It is heartening to know that nanotechnology has the potential to make a positive social contribution in an area it is not normally associated with, by helping to solve more crimes.

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DOI: 10.1016/S1369-7021(09)70167-1