CLPEX Chat Board

Hi everyone,

I have had success soliciting help from members of the Board before when I have run into photography issues, so I thought I would try again. I have developed ridge detail using LCV on a wall from a homicide scene. I photographed the ridge detail at the scene after appyling LCV, and then applied amido black to the wall. There was no further development of the ridge detail. Before we left the scene, I asked to have that piece of wall cut out so that I could take better photographs back at the lab.

Upon returning to the lab with the piece of wall, I have tried several different filters to try and minimize the interference with the background. The wall is textured, and in addition, has a brown faux finish to it, complete with lots of brush strokes, and different shades of brown and white. Although the color photographs are okay, I would like to find a better way to capture the ridge detail. I have used purple, yellow, orange, red, green, blue, fluorescent, and no filters to photograph the latent. I have also used PhotoShop CS2 to try and reduce the background interference.

Does anyone have any further ideas? I am planning on trying to use our Polilight tomorrow to see if it will fluoresce at all. We tried our RUVIS and couldn't see anything. The ridge detail was not visible prior to the application of LCV, and there has been no swabbing of the potential blood (until I have finished trying to capture the ridge detail).

In addition, I was wondering if anyone has a suggestion as to further chemical processing possibilities. The amido black tech notes we have in the lab suggest physical developer, but it doesn't distinguish if that is only appropriate if the impression is on a porous surface/item, or if it can be used on non-porous surfaces too.

Any help is greatly appreciated. I am including a photograph of the wall to show what it looks like...

Thanks!

Heather

Heather,

Do you know anyone in the Mesa area who has either one of the Fuji UV/IR (IS Pro) cameras, or a digital camera modified for IR use? With one of those cameras and a selection of IR filters, you may be able to capture the ridge detail in the IR while eliminating the background color.

One thing that probably makes Photoshop enhancement difficult is that the texture is causing all sorts of reflections into the camera. So the reflections are a different color than the background itself. What kind of lighting are you using? If it's direct, you may want to try and diffuse the lighting. If you've got custom cones or tents you can use them, or some white sheets or paper can also do the job. Just surround the area with a cone made from white paper with a hole for the lens to go through and then aim your light source(s) at the cone.

Here's a picture of how a light tent was made using a pvc pipe framework and a sheet:



This may cut down on the reflections that you're battling.

Catalytic reactions of LCV and crystal violet will fluoresce with a 532nm diode or yag laser - around 1 watt at the wand, and eliminate background, but the subsequent application of amido black will probably squelch any available fluoresence.

Maybe worth a try however.

Hi Steve and Ducky,

Thank you for the suggestions. I am going to check around to see if anyone has the new Fuji camera. I know that many of the agencies were given demonstrations, but I don't know if any actually purchased the camera.

As far as the lighting, we did direct and diffused lighting. We have a dome that we were able to use. The photograph of the latent is nice and sharp, there is just more background interference than I would like.

I'll attempt to use the Polilight to see if any of the detail will fluoresce.

Are there any other chemicals that I can try that could further develop the ridge detail?

Thanks again!

If you’re planning on swabbing the print after you are finished processing it, you may want to try the Subtraction Method (after you have tried all other means) since it can give you great results at the cost of destroying the latent.
The Subtraction Method is done by taking a photograph of the latent and then making sure not to move the camera or lighting or object erase the print and take another photograph. You then go into calculations and put one image into the Source 1 field and the other into the Source 2 field, select the green channel for each, select subtract in the Blending drop-down and adjust the Offset anywhere from 50 to 70. Photoshop is essentially looking at every pixel in the image and looking for a difference, which if you did not move the lighting or camera should only be the hard to see latent. It is a fun thing to try out if you have never done it before.
Good luck,
PG

Peter is right about using image subtraction, although it is much easier to do this by stacking the two images as layers and changing the blending mode to Difference - you can still isolate specific color channels while doing this, and it's much more intuitive.

If reflections are a problem, you might also try cross polarization lighting. You can purchase large sheets of polarizing filters and use these on your lights in one direction, then use a polarizing filter on your camera in another direction. You can eliminate all reflections this way.

Good luck,

George