CLPEX Chat Board

With regards to the development of fingerprints on currency.

I know it is difficult to develop fingerprints on currency due to the fact that it is in wide circulation. However I have noted that people have given suggestions for different concentration and application of Ninhydrin but no one has really mentioned what happens to the notes after treatment apart from placing items in bags and leaving them for an undetermined amount of time.

Do you have a nin 'oven'?

In our lab we have specially designed 'oven' for ninhydrin treated items. It is set at fix level of heat and humidity and items are left in the 'oven' for four minutes. We get very good results using this and I have treated four different currency jobs today and have developed some marks on each job and these are not isolated cases.

(In tests we have found that to get the same results we get using the 'oven' we have to leave items to air dry for 7-10 days).

I hope this is of help.

Have you considered vacuum metal deposition?

This project was conducted a few years ago at UTS in conjunction with the AFP to solve the problem of fingerprint development on our semi-porous Australian polymer banknotes that do not develop fingerprints well using techniques designed for porous or non-porous surfaces.

There were several references in the journal Forensic Science International that might be of interest to you. Let me know if you are interested and I'll chase them up for you.

Kind regards,
Shaheen Aumeer-Donovan

Joe T, do you have any information on the cost of the humidity ovens?

If I remember right the one we purchased and had installed ran about $8,000 in US Dollars. I was wondering if there were cheaper versions. The hard part to ours was connecting the de-ionized water to it, and then a way for the excess humidity to be drained off into a sink.

Shaheen, do you have any information on the cost of the equipment for Vacuum Metal Deposition?

The last time we looked into it, it was around $60,000 in US Dollars. I was wondering if the prices may have gone down.

Also if I remember correctly the US has not gone with polymer banknotes yet, but they are considering it.

Thanks,

Charles,

the oven you have mentioned sound the same as the one we use now which is a FDC185. We purchased it from Sanyo Gallencamp in the UK. Tel 01509 265265 but I am sure if you put the name on the internet you can find out if they have a sister company in the US. We paid about £5K for a new one about 3 years ago so prices would roughly be same as you paid for a previous machine.

We had to temporarily close our lab no long ago for repairs and we set our oven up on a bench in another lab. We had a bucket 'run' on the bottom (using garden hose) instead of a sink and fed a 10 gallon drum of ionised water into the machine and it worked just as well as when it was fed to the water filter and drain in the main lab.

Handling of widely-circulated currency is not always the only source of contamination. Many years ago, someone from the U.S. Dept. of Treasury told me that one of the ingredients in paper sizing used on U.S. currency came from animal fat, which contains amino acids. My experience has been that even uncirculated U.S. paper currency has the potential to exhibit background problems with the application of ninhydrin.

Heat accelerates the ninhydrin / latent print development process, or may be considered as compressing the time required for development. While this is ordinarily an advantage, there is evidence that it becomes a disadvantage in the case of U.S. currency.

The visible development of latent print residue appears to be relatively faster (due to a higher concentration of amino acids recently deposited?), than background interference. A slower development timeline may allow documentation/photography of the latent print before background development has a chance to overwhelm the print.

That being said, my experience with a laboratory oven including controllable humidity is limited. I'd be interested in hearing about results with U.S. currency.
Regards, RLT