CLPEX Chat Board

Does anyone know of any studies that have been done involving the enhancement of bloody prints on cloth? Any help would be greatly appreciated.

In training I used Amido Black to enhance the bloody print and with digital enhancement, specifically a pattern removal filter, was able to get identifiable prints. That was a on a piece of cotton. Recently someone in my agency used Amido Black to obtain and enchance some visible blood prints on a jacket.

Amido is a poor choice for cloth materials as this is a general protein stain that requires metanol rinses to attempt to remove the dark background staining, thereby loosing contrast.
Leuco Crystal violet is a heme catalytic reaction with no background stain on cloth. It converts the clear reagent to purple on only the blood impression. High in contrast and the impression will also flouresce at 532nm so it can also be used on black cloth. Rinse with distilled water to prevent subsequent background oxidation of non reacting reagent.

Whether or not Amido Black is a ‘poor’ choice is dependent on your particular situation. Two problems with Amido Black are the disposal of the chemicals (if you’re using the methanol based version) and it’s not particularly useful on dark fabrics. If these things aren’t a problem in your particular case then Amido Black is just a different choice from LCV, maybe not a ‘poor’ choice.

There are several cases where Amido Black has been successfully used in developing identifiable latent prints on fabric (like State of Washington v Eric Hayden and State of Ohio v Hartman). I’ve never tried LCV, so I can’t compare the two methods but I have seen Amido Black in action and I like it.

You should refer to the JFI. I don't think there has been any actual studies done, but there are a few published case reviews talking about different processes. I wrote an article for the JFI a few years back.

“Identification of Blood Prints on Fabric Using Amido Black and Digital Enhancement” Journal of Forensic Identification, Volume 50 (#1), January/February 2000, (pp.20-32)

Amido black will work, however it is a poor first or only choice for enhancement of blood impressions on a porous surface.

Since Amido Black is both a permanent stain and a general protein stain, things to consider are:
1. How much blood is there to react and how porous is the fiber? (i.e. cotton vs. nylon)
2. Is there any trace evidence, hair, fiber, or biological that will be damaged by the staining?
3. Is there any protein other than bloods that are invisible but may also react and obliterate the blood impression?

Like physical developer Amido Black is the last step in sequential processing. Amido Black can work in sequence with a hemoglobin specific reagent such as Leuco Crystal Violet (LCV) since they target two different things; blood and proteins. LCV will react only with the blood and will ignore food products and other proteins that may be present on the fabric but not visible. Amido Black then can be used to darken the impression if needed by only reacting to the protein.

The opposite scenario of first using the protein stain Hungarian Red and then using LCV to darken the red reaction of the protein stain is also possible.

LCV is desirable as you can get both a color contrast with the background and a florescence from the same reagent and it can be used on both porous and non porous surfaces. LCV also has a instantaneous acid blood fixative that does not require methanol fixing of the impression.

A evaluation study paper on blood reagents and a PowerPoint with images is available at this site
http://www.latent-prints.com/processing_techniques.htm

Don't forget your imaging technologies here as well. The weave pattern can be distracting with these prints. The weave patterns can be reduced using several techniques - including simply blurring them; or, using a directional median filter; or, using an FFT filter. The choice of tool is depentant on the features of the print and the weave pattern.

George