CLPEX Chat Board

Hi all,

I have asked a couple of others about this, but thought that posting here might elicit something we haven't considered. I am currently processing a tv tray and a shower curtain liner in the lab. There is a large amount of blood on the shower curtain liner, and there is some blood on various portions of the tv tray. The tv tray appears to be semi-porous (coated, but not really lacquered). I bought a similar tv tray, cut it into a couple of pieces and did some experimentation (CA first, then ninhydrin, then LCV). The second piece was not superglued (just ninhydrin has been applied at this point). It seems that there is some interference with the success of the blood reagents when CA has been used first. Has anyone else had this problem?
Basically, I would like to process this surface for both latent blood impressions and regular latent impressions, but I am concerned that I may destroy some latent impressions. If I do CA the tray, will I lose potential bloody impressions? If I don't CA the tray, and use blood reagents on the entire surface, will I lose regular latent impressions?
The dilemma with the shower curtain liner is the same. I bought a similar liner, cut it into pieces and experimented. If I used CA first, the blood impressions did not seem to develop as clearly as those that had not been superglued.

Thoughts, opinions, suggestions?

Thanks!

Heather,
How much time has passed since the crime (or when blood/latent prints of interest was deposited)? Is the shower curtain vinyl plastic?

Have you considered magna powder? I have had success in the past with magna powder (preferably sifted & matched to the substrate porosity, texture & other properties), instead of CA. Also had good success with follow-up blood enhancers. I actually preferred ninhydrin when the substate allowed its use, though doubt that would be best from your description of the evidence.
Regards, RLT

The blood is about 2 weeks old, and yes, I'm pretty sure that the shower liner is vinyl plastic (it is pretty heavily textured).

In my opinion, the age factor would lead to more consideration for magna-powder, however the texture on the shower curtain would lead to more consideration for CA. Would have to see the actual surfaces & know something about environmental factors for a more definitive opinion.

Back to a couple of your original questions: Yes, I have noticed a degradation of results when applying a blood reagent after CA, although the tradeoff can be acceptable. if you don't do some kind of processing prior to the use of a blood reagent, you definitely run a risk of losing latent prints. Have you ever had a visible print in blood, took your photographs, and then processed for unseen latents? If your experience is similar to mine, more often than not, additional latent prints were developed. The same principle would apply. (I'm sure you already knew that, however there may be less experienced people reading this thread).

If a decision is made to use a blood reagent first, a methanol carrier tends to 'fix' blood prints in place, however 'oil' or 'grease' latent prints have a better chance of surviving application of a blood reagent in a water carrier.