Forensics Questions

[forensicsresearcher]

Hello -- I'm a writer with a couple forensics questions. Sorry if these sound a bit macabre, but it's purely for fiction purposes, I swear.

 

1) Is there any way to detect blood with household chemicals? I know that crime scenes use luminol or phenolphthalein, but -- as far as I know -- there's no moderately easy way to mix up a homemade batch of anything comparable. Preferably, I'd like a way for a forensically knowledgable protagonist to detect traces of blood that have been wiped away from a surface without the help of a blacklight. Any way to do this? Any easy substitute for phenolphthalein?

 

2) Somewhat related to question one, I read somewhere that if you put a cloth that has a blood stain on it into a glass of hydrogen peroxide that the hydrogen peroxide would start bubbling because iron in the red blood cells catalyze the decomposition. Would this work if the blood stain were on a piece of wood, or metal, or some material other than cloth?

 

3) Do recently deceased corpses give off heat before they cool down? If so, how much? If a person died outside in the winter, would it be enough to melt some of the snow around them?

 

4) Does any scientific story or neat trick come to mind of how chemistry has been (or could be) used to gather criminal evidence? For example, I've read that the younger a person is, the faster their hair dissolves in lye (could be useful in solving a mystery case).

 

Thanks, looking forward to some interesting answers.

[Dr. Monte Miller]

I was a previous crime scene investigator and biology/DNA expert.

 

 

1. There are chemicals other than the one you mentioned that will detect blood. No household chemicals can be used. Even the ones that we do use only presume that there is blood, further testing must be done. It would be difficult or impossible for a lay person to test for. A chemist could come up with something, or perhaps somebody could have read something, but a lay person with no specific knowledge could not.

 

2. Yes it would bubble, but just about anything in hydrogen peroxide will cause it to bubble.

 

3. Yes they give off heat during decomposition, not sure about the temperature. They would melt a little snow, not much. The cool outside temp would whisk away the heat almost immediately. The body would freeze and more likely be preserved rather than melt slow, the decomposition would be slow so the temp would really not rise.

 

4. Chemistry is used daily at crime scenes, so yes it is used. They are all neat tricks. Chemistry and physics are used in all of the analysis of samples, from trace evidence to DNA to drugs. Most of these use sophisticated machines to detect exact amount. Shelock Holmes uses neat tricks, but in reality we don't use them in a crime lab.

 

mmiller@forensicdnaexperts.com

Edited July 21, 2011 by swansont
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[John Cuthber]

Phenolphthalein is available on eBay, but it won't help you directly.

The test for blood uses phenolphthalin which is a bit different. IIRC you can make it from the phthalein by reduction with zinc dust in alkali.

http://en.wikipedia.org/wiki/Kastle-Meyer_test

 

Why do you want to know?

[forensicsresearcher]

Thanks for the responses. As I mentioned, I'm just a writer who's trying to use some chemistry in my mystery/thriller novel. The idea is that my main character is in a place where they suspect a murder happened and they need to quickly detect if there are any traces of blood on the floor (the murderer mopped it up). They don't have any professional presumptive tests on them, so they idea was to quickly create one with chemicals found around the house.

 

I had one person suggest the following (tell me if it could work... I'll probably have to take huge creative license anyway):

To create a homemade LGM test, combine malachite green (found in aquarium stores), acetic acid distilled from vinegar, and zinc (apparently US pennies are made of zinc). I know it's a longshot, but, in theory, could it work to combine malachite green, acetic acid, and a couple pennies to make an impromptu LGM test? Any other suggestions?