CLPEX Chat Board

We currently do a presumptive test for blood before we process for latent impressions. There is debate in our laboratory whether this is necessary. Our chemicals that are currently approved for processing impressions in blood are amido black and ninhydrin. What are the stances on this issue? Any feedback would be much appreciated. I should add that these are cases that do not require biological evidence collection or analysis.

Both of these are not specific to blood. Ninhydrin is only for amines and amido black is a general protein stain.

You can use heme (blood) specific catalytic reaction processes that can be both presumtive and enhancing in one applicaton. Choice is based upon the color of the background for enhancement or flourescent reactions.

Leuco Crystal violet, Merbromin, Fluorescein to name a few.

Thanks for the response. I should clarify. We do not presumptive test with ninhydrin or amido black. We use phenophaline (spelling) or o-tal. The problem is should we process an item presuming that something looks like it has blood on it without having anything else to go by then "it looks like blood". Will amido black hinder other possible processes that could be utilized in latent development if there is no blood present? I would not think it would on a non-porous surface, but I am open to other thoughts.

Heme is a good suggestion. I will look into that.

Are you performing a presumptive on possible blood, then using Amido black as the first processing technique? On a non-porous item, you may want to perform SG fuming first as to "lock" on any ridge detail before treating with Amido Black as the rinsing process may wash away latent detail.