Jan 31, 2011

Criminal Touch

Some day in the near future criminals might be convicted because they touched their victim.  No joke.  A new study released late last year revealed a breakthrough use for a current technology that has major potential to put bad guys in jail.  The technology is called vacuum metal deposition or VMD for short, and it has already been used to put some high profile criminals behind bars (see Richard Rogers "Last Call Killer").  However the new use for the technology is to find fingerprints on clothing.

VMD is performed in a two stage process.  The first stage involves vaporizing a small amount of gold onto a surface under high vacuum.  The gold penetrates into the surface by a small amount.  The next step is to vaporize a more significant amount of zinc and apply to the surface under high vacuum.  What remains is a visible print where the zinc deposits everywhere on the surface except on the ridges themselves (effectively creating a fingerprint negative).

This technology normally used on plastics and smooth surfaces was tested with four different materials: nylon, polyester, polycotton, and cotton.  The researchers were able to obtain identifiable prints on the smoother non-porous fabrics such as nylon, but were only able to get outlines of prints using cotton.  Thus next time you go out and plan to get mugged, wear nylon. 

The technique could prove to be a helpful tool on the fight against crime, even when used on cotton where an outline of a hand print can be found and used to look for DNA evidence.

This technology further enters Biometrics into the crime scene making it harder and harder for criminals to get away with their mischiefs.


Original Article:
Joanna Fraser, Keith Sturrock, Paul Deacon, Stephen Bleay, David H. Bremner. Visualisation of fingermarks and grab impressions on fabrics. Part 1: Gold/zinc vacuum metal deposition. Forensic Science International, 2010; DOI: 10.1016/j.forsciint.2010.11.003


  1. FASCINATING post--nice link to current research. And the blog design looks beautiful.

  2. This is cool, Carlos. I know the "gold" usage is probably minimal, but does that still make this an expensive procedure?

  3. I really like your design and also how you can put this technology into a few short paragraphs. It is very easy and enjoyable to read

  4. Do you know if fingerprints decay on different fabrics, like natural fibers for example?

    Also, do you know how this is recieved in trails? Because I can see the defense arguing whether the touch, when the suspect left the print, was malicious or not.

  5. I'm also curious about the limitations. Fabrics naturally have wrinkles and textures that may cause fingerprints to either be incomplete or skewed in some fashion. I would imagine that a defense may be able to use the same technology to prove that a wrinkle in a fabric would cause significant credibility threats to the prosecution.

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  7. @ Zack- Yea I think the procedure could get pretty expensive. The machine that actually does the VMD cost about $100,000. I could not find how much gold they actually use but they have to use >99% pure gold, so it must be pretty expensive, but it's worth it to catch a criminal right?

    @J.D & Cold Steel- You are right that this technology is not extremely useful for the identification of the subject but it could be used in other ways. For example if they are able to find where the grab was they could look for DNA there and there is a high chance that they could find it. Another thing is it could be used to detect if a person was pushed or grabbed based on the way the print looks. As far as how long fingerprints last, they were able to detect prints up to about 28 days later on nylon, and considerably less on cotton and others. The picture from this article is actually a print on nylon that is 21 days old from the article.

    @Jen & Michelle- Thanks for the comments!