In the name of security, societies from around the world are struggling to define the line between surveillance and privacy. Iris recognition scans identify us by peering into our eyes and taking advantage of the uniqueness of an inner human body part. What would you say if there were a surveillance machine in use that can actually see through us and does perform the electronic equivalent of a strip search? Would you feel violated? The use of such a machine would certainly raise privacy issues.

The technology is called 'Backscatter X-ray' and is an advanced imaging technology. It is one of two types of whole body imaging technologies being used to perform full-body scans of airline passengers. On the positive side, this machine could be used to detect hidden plastic weapons, explosive devices, drugs, currency and other contraband not picked up by other X-ray inspection systems. However, it raises privacy concerns in that the image of the subject appears as a nude picture except perhaps for the explosive device hidden on the body.

Backscatter can already do more than screen people. It can be used for cargo and vehicle inspection. There are companies that manufacture mobile, relocatable and fixed site inspection systems. These configurations would be ideal for inspecting cars, vans, trucks and air and sea cargo holds for concealed threats and contraband.

While it works in ways similar to x-rays, backscatter reveal things that regular x-rays miss. Backscatter technology is based on the X-ray 'Compton Scattering' effect and the backscatter systems work by shooting high energy electronically generated light beams at an object. The backscatter image captures data from X-ray photons that are scattered from the object undergoing inspection. X-ray photons scatter differently when they encounter different types of materials. Compton scattering is material-dependent, with the lower atomic number materials scattering more strongly than the higher numbered ones. Organic matter, specifically explosive material, contains low atomic number elements such as carbon, oxygen, hydrogen and nitrogen.

These high energy beams penetrate dense objects like metal but bounce and scatter back when they hit low density materials such as explosives, drugs, cigarettes, and people, especially when hidden within a complex environment. How the light particles scatter back reveals the shape and form of objects providing the context and clarity to expedite inspections.The technology creates clear, uncluttered, two dimensional, photo-like X-ray images which permits the analyst to accurately and quickly interpret the images provided. It also produces these images while emitting a substantially lower radiation dose to both the cargo and the environment.

For example, viewed with a regular x-ray machine a truckload of fruit may not arouse suspicion. By directing a sweeping beam of X-rays at the truck, a backscatter machine would reveal traces of drugs or people if present. You can see why,if deployed on borders around the world, backscatters would be a powerful deterrent to smugglers. This technology would help to reveal things in an instant that would take a border guard hours to find.

The is the argument is that this technology can be invasive. Privacy advocates are concerned because it implements a virtual strip search providing authorities with an image that leaves nothing to the imagination. British officials are concerned that the use of such scanners to scan children may be illegal. We also have the argument from different cultures about modesty issues and how they contravene their religious beliefs. It is true that this technology is invasive but the fact is that these machines are assisting authorities to tighten security where it is needed most.