The Amido Black Blood Reagent
There are a number of other blood reagents like Luminol, Fluorescein, and Leucocrystal Violet that seem to be much more commonly referred to in literature and on television but Amido Black is another one you might consider using in your story. Amido Black is a presumptive blood reagent (can’t discriminate between human and non-human blood) that is very useful in developing diluted or latent blood impressions like shoe prints. This makes it an effective tool in the bloodstain pattern analysts arsenal. Amido Black is a water or methanol based dye stain that reacts with the proteins in blood turning them a dark blue-black color). The process begins by “fixing” the possible blood impressions with a methanol wash prior to the application of the reagent. Sometimes this methanol is mixed directly with the reagent at the time of application. The solution can then be sprayed or poured over the testing area. Some smaller items of evidence can be “dipped” in trays of the reagent as well. The reaction may not be as “flashy” as one of the luminescent reagents but it can be just as effective.
The sensitivity of the reagent is thought to be about 1:10,000 (parts per blood dilution) and has no detrimental effects on subsequent DNA testing although if too much reagent is “washed” over the evidence the sample could become too diluted for DNA testing. It can be used to detect any latent mark (such as tire print, shoe print, fingerprint, or tool mark) in blood at the crime scene. Once the reagent is applied and the blood impression is developed then the visible impression needs to be “fixed” with a 5% sulfosalicylic acid. The print can then be photographed.
I have successfully used this reagent many times at crime scenes and in the laboratory. It provides exceptional detail provided there is contrast with the background. That is the one potential problem with this reagent. Because it turns the blood a dark blue-black color, you can’t use it effectively on dark colored surfaces. That is something you’ll want to keep in mind if using this reagetn in your novel. The video below presents a homicide case in which Amido Black was successfully used to develop bloody shoe impressions from the suspect at the crime scene.
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Posted on February 24, 2012, in The Crime Laboratory, The Crime Scene and tagged Amido Black, blood reagent, Bloodstain Pattern Analysis, BSPA, Crime Scene, csi, detective, fiction, Fluorescein, forensics, Luminol, murder, mystery, police, thriller, tom adair. Bookmark the permalink. 4 Comments.
Tom, you must be psychic. ( : I had a question on blood analysis that came up in the edits my editor sent back and I went to your posts that I had saved. I found one on Luminol you had written and then you write this one. My story is a paranormal romance. The female protagonist is a police officer in San Diego. It’s a long novella and more focused on the paranormal than police procedure but my editor wanted more detail.
If my detective looks down on the ground and spots rust-colored spots she thinks is blood, does she think along the lines this looks like blood but I need forensics out here to check it out. Or I need forensics out here to run XXX test? I think I simply changed what I had to saying it looked like blood but forensics would have to analyze it to be sure. Any guidance is most appreciated.
Hey Gabriella, I knew you’d be calling…:) Really old blood can sometimes be mistaken for rust spots, coffee stains, cola stains, even red paint but more often than not blood is pretty recognizable to experienced analysts. You can’t go to court on your observations only though so you have to run tests. There are a number of presumptive field tests that some detectives carry with them. one such test is Phenolphthalein (pronounced fee-no-thay-lean). To conduct this test the detective would put a drop of distilled water or saline on a cotton tipped swab and swab the suspected blood stain. Then they would add a drop of the Phenolphthalein reagent. Then they would add a drop of hydrogen Peroxide. If there is an “immediate” flash (color change) to pink then the stain is preseumptive positive for blood. There are other tests like hemistix which act in a similar field testing manner. Ultimately, the detective would need to submit the swab/sample to the DNA lab to determine if it is human blood (although there is a field test for that as well) and create a profile of the donor.
When I instruct students about unknown stains or reaction areas I try to get them to focus on the shape and distribution of the stains. Do they look like they could be bloodstains? Would blood act in that manner? Where is the location of the stain? If it is along the center console of a motor vehicle it could be blood but it could also be other dark colored liquids like cola that may have spilled during the operation of the vehicle. So they have to not only look at the stain the but contect of the stain in relation to it’s surroundings (holistic huh?). Does that help?
This does help, thank you. So it sounds like detectives might keep some kind of simple testing kit that they can use on the go. Is that right? In this story, police procedure is at a minimum since the focus is on the paranormal, but I am collecting everything you write because it is all extremely useful.
I’m in Japan and my husband and I like to watch a series called “Kassoken no Onna.” It translates to Scientific Research Investigation Woman, or something like that. It’s a bit glamorized for TV, but for example whenever there is a blood stain, they show them throwing over a black tent and then using a kind of ultraviolet light to see any blood stains. I think they are supposed to be using Luminol, though I’m not sure. The other week I learned something new when the had a mystery in which there was no body but a huge blood stain on a bed indicating a murder had likely taken place given the amount of human blood, which they confirmed. The blood was AB-. Further examination of the scene discovered trace amounts of B- blood. The assumption was the victim was AB- but somehow the murderer was nicked in the struggle and was B-. Of course none of the suspects had B- blood. Turned out the victim was a blood chimera, carrying two blood types. I had to look it up in English because I had never heard of that one before. Unfortunately, because of the language issues, I usually don’t catch all the scientific explanations, but I’m enjoying the series and it’s fascinating to see the possibilities of what science can do.
Sorry, for the ramble. ( : I do appreciate all the help and I’m going to tweak my edits some more.
Talk to you soon!
Not a problem, sounds like an interesting show. Yes, SOME detectives carry presumptive blood tests with them while on-call or responding to crime scenes. This is more likely to be true if the detective has training in basic bloodstain pattern analysis or homicide investigation.