Notices
Results 1 to 4 of 4

Thread: Forensics Questions

  1. #1 Forensics Questions 
    New Member
    Join Date
    Jun 2011
    Posts
    2
    Hello -- I'm a writer with a couple forensics questions, and I'm hoping that this forum can help me out. Sorry if these questions sound a bit macabre; 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


    Reply With Quote  
     

  2.  
     

  3. #2  
    Forum Cosmic Wizard i_feel_tiredsleepy's Avatar
    Join Date
    Mar 2008
    Location
    Montreal
    Posts
    2,256
    Peroxide fizzes in the presence of blood because of an enzyme called catalase that breaks the H2O2 down into H2O and oxygen free radicals, which rapidly bond with another oxygen to form O2 that creates the bubbles. Dried blood won't fizz because the catalase breaks down fairly rapidly, I'm not sure of the half-life off the top of my head but unless the blood is fairly fresh I don't think you would get bubbles.


    "I almost went to bed
    without remembering
    the four white violets
    I put in the button-hole
    of your green sweater

    and how i kissed you then
    and you kissed me
    shy as though I'd
    never been your lover "
    - Leonard Cohen
    Reply With Quote  
     

  4. #3 Re: Forensics Questions 
    Reptile Dysfunction drowsy turtle's Avatar
    Join Date
    Mar 2009
    Location
    UK
    Posts
    2,256
    Quote Originally Posted by forensicsresearcher
    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?
    I'm not sure if this is what you're after, but red blood cells are reasonably distinct under a microscope.



    You could get a hold of a good enough microscope for a couple of hundred /$. For a wiped surface, you could use clear advesive tape orsomething to remove any remaining blood cells from the surface, and then attach this to a slide.

    Just a thought; I'm sure someone will tell me why it won't work...

    Quote Originally Posted by forensicsresearcher
    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?
    The amount of heat given off will depend on the size of the person. Taking an average 65kg person, and estimating the specific heat capacity as the same as water, they will give off 273 kJ of heat energy, which would only melt (at most; less if the snow is colder than 0 degrees celcius) 0.8 kg or so of snow.
    "The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair." ~ Douglas Adams
    Reply With Quote  
     

  5. #4  
    New Member
    Join Date
    Jun 2011
    Posts
    2
    Quote Originally Posted by i_feel_tiredsleepy
    Unless the blood is fairly fresh I don't think you would get bubbles.
    Drats.

    drowsy turtle: Although I was looking for a chemical way of revealing/identifying blood stains, this tape method is pretty creative. Can anyone else confirm or deny if this would work?
    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •