Methods for making prints for ninhydrin study?

[Debs McDonald]

Hi, this may seem like a strange question but would anyone be able to tell me how they prepare fingerprints for deposition on paper when studying ninhydrin? There seems to be so many variables that need to be considered when trying to make reproducible, but realistic prints. Can anyone refer me to studies that go into detail about their fingerprint deposition method? Or studies that address this directly?

Any advice you could give me would be greatly appreciated.
Thanks,
Debbie

[EmmaC]

During my research for my dissertation I have found a few journal articles that go into charging up the fingers with sweat but none on pressure.

Basically to charge the fingers up with sweat - rub the finger you are going to be putting on the paper on your T-zone and through your hair. If you create a method where you rub the finger a certain number of times on one area, then on another and so on.

eg. 3 times on the forehead
3 times on the cheek
3 times on the cheek
and then 3 times on your scalp.

Other than that I am still working on finding the pressure needed for the perfect print. One of our Phd students at the university has done a lot of work on the best way to produce a print with good 3rd level detail. When I contact him I will ask him for the best method and pass it on to you.

Email me at EmmaClemson@blueyonder.co.uk and I'll try and pass on all my journal articles that I have found.

[Amy Hart]

While I don't have any journal articles regarding the creation of ninhydrin prints, I can give some practical advice.

If you want purely sweat prints for your study:

1. You can find a consistently sweaty individual to donate your prints (there's always one around somewhere).

2. You can wear some gloves on your hands for a length of time before attempting to donate prints.

If you just want prints that will react fairly consistently with ninhydrin, you can apply a light coat of hand lotion or saliva to your skin. Both will usually have enough amino acids in them to react well with ninhydrin.

[Ernie Hamm]

You have received information on source areas for acquiring substances to ‘make’ latent prints that will react with a ninhydrin solution. The ideal amino acid sources are sweat and saliva. Several of the areas mentioned are more favorable for body oil (sebaceous) residue with amino acid matter being secondary and incidental. A lot of agencies have those fortunate (unfortunate?) individuals that can be called upon to provide latent prints to test or evaluate ninhydrin (and other) reactions. Even as tried and true as this method may be, there can still be unknown variables relating to the amount and type of amino acid material being deposited at any specific time. There are commercial products available that are essentially fingerprint pads that contain amino acid solutions that will provide a consistent coating to the finger that will react to ninhydrin solutions. There are pads with amino acid material and also pads containing sebaceous matter. These were designed and developed to allow agencies to document and validate reagent efficiency prior to evidence processing without looking around for that ‘special’ volunteer. An advantage of these prepared solution pads is that the delivered residue is consistent from one deposit to another and eliminates variables from multiple donors or a single donor at varying intervals, if that is a desired element of the evaluation.

Hope this helps.

Terry, patience, sometimes something else gets through.

[RL Tavernaro]

Depending on what your specific needs or goals are in studying ninhydrin developed latent fingerprints, one method that might be useful is beef bullion broth as a deposition medium.

If memory serves correct, 2 cubes in a cup (8 oz) of water (boiled & reduced to a broth) serves as an adequate source of reasonably consistent amino acids. The broth should of course be cooled to a safe temperature, and then fingers can be dipped in, air dried, and then applied to the paper (?) surface.

If the paper is placed on a postal scale or similar, consistent pressure may also be monitored.

I am not aware of any comprehensive study on human perspriation, eccrine and/or apocrine secretions, along with common external contaminants specifically related to ninhydrin reaction. It would seem that a representative population group would need to be developed, with secretions collected and tested for chemical constituents as an initial baseline step. Further steps would depend on the research objectives.