CLPEX Chat Board

We at the MN BCA have been taking a closer look at how we have been enhancing bloody prints both in the lab and when responding to crime scenes. We are looking into how fixing/denaturing can be accomplished when using protein stains such as coomassie blue and amido black. We have found many sources that state different methods of utilizing these stains. Some that don’t mention fixing/denaturing at all, saturating/immersing the item in methanol for anywhere from 2 minutes to 1 hour, or baking/heating @ 100oC for anywhere from no time specified to 30 minutes and up to 1 hour. Some of these methods are difficult to perform while at a crime scene and taking back to the lab is not plausible (such as a bloody print on a wall). We were wondering what the SOP’s of others in the field are for the fixing/denaturing step and what their sources are for that step. Due to ASCLD, if the SOP’s state using heat at 100oC for 1 hour, we need to be able to measure that in the field which is not really practical.

We are also going to do some of our own research comparing blood enhancers such as coomassie blue, DAB, amido black, and leucomalachite green. If anyone uses or knows of other blood enhancers that are worth taking a look at please let us know. You may contact me at:
Justin.Bundy@state.mn.us

Thanks for any help,
Justin Bundy.

Hi Justin,
There are several blood enhancement reagent formulas that utilize sulfosalicylic acid as the fixative and it is built into the regent formulation. I seen others which utilize citric acid. You can get access to some of these formulas in the FBI's Chemical Formulas and Processing Guide for Developing Latent Prints put out by the U.S. Dept. of Justice.
When using methanol as a fixative or in methanol based formulations, you have to be sure the surface being processed will not be damaged by the methanol. Methanol will eat through paint and polyurethane finishes!
I suggest you include leucocrystal violet in your reagent list. Hope this helps! Chris

The heme reagents are more sensitive than protein dye stains. I use tetramethylbenzidine (TMB) on most surfaces and 0-tolidine on surfaces that are the same color as TMB (green). I've compared them to Amido Black, Hungarian Red, Leucomalachite Green, Leuco Crystal Violet, and others. I like the TMB best. However, TMB is somewhat difficult to make, has no shelf life (just a day), and is a carcinogen. Yet, despite all that, I still prefer it.

I noticed that you use O-tolidine. There are not that many agency that use O'tolidine for safety reasons. I was actually trying to find out information about O-tolidine, specifically if one can still do an additonal test for presence of blood after having used O'tolidine?

0-Tolidine is a heme reagent, and as such, IS an excellent presemptive test. Heme is not found in anything but blood. If, after treatment, you fail to notice any reaction, that would indicate there is no blood there.

Not only is it a usable presumptive test for blood - it is extremely sensitive. However, all animal blood contains heme, so it will react to all animal blood.