Arson investigators: intro to LiDAR class questions

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scottgrieve
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Re: Arson investigators: intro to LiDAR class questions

Post by scottgrieve » Mon May 13, 2019 7:34 pm

James Hall wrote:
Thu Mar 01, 2018 3:25 pm
Investigative

Urine, chemicals, salts, areas where paint has been removed and other residues can be seen in laser scans because it can change the light reflectively of the surface. For me it is most often seen on concrete. I've identified non visible paint stripes on airport runways by adjusting the display characteristics in Cyclone. When we scan a parking garage, we pick up all kinds of stains, oil , salt, and urine mostly.
I'm not a forensics guy, but looking at how different substances affect your scanned surfaces might be useful for your discussion.
James,
Hi James,

Your findings here are really interesting. Forgive me I am not massively clued up in the capabilities but do you think it is possible pick up different residues after they have been burnt? for example in a arson case, a burnt wall vs a burnt wall that had blood or ignitable liquids before

Best Wishes,
Scott

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Re: Arson investigators: intro to LiDAR class questions

Post by James Hall » Tue May 14, 2019 3:58 pm

Hello Scott,

This sounds like a great test. I do not know how fire would effect blood or the residue of ignitable liquids. You would also have to consider the composition of the wall; concrete, wood paneling, painted gypsum board would very depending if the substrate is consumed or if only the blood is burnt or just heated.
My Initial guess would be charring and soot would make it hard to detect the residue, as black is the hardest color for a laser scanner to pick up. The area with the residue would also have to larger then laser dot on the surface. Something like a two squarer centimeters to make sure you can see the results.

To answer your question. Yes I think it is possible to detect residue on some surfaces after a fire, but am unsure to the extent.

James,

scottgrieve
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Re: Arson investigators: intro to LiDAR class questions

Post by scottgrieve » Thu May 16, 2019 10:47 pm

James Hall wrote:
Tue May 14, 2019 3:58 pm
Hello Scott,

This sounds like a great test. I do not know how fire would effect blood or the residue of ignitable liquids. You would also have to consider the composition of the wall; concrete, wood paneling, painted gypsum board would very depending if the substrate is consumed or if only the blood is burnt or just heated.
My Initial guess would be charring and soot would make it hard to detect the residue, as black is the hardest color for a laser scanner to pick up. The area with the residue would also have to larger then laser dot on the surface. Something like a two squarer centimeters to make sure you can see the results.

To answer your question. Yes I think it is possible to detect residue on some surfaces after a fire, but am unsure to the extent.

James,
Hi James,

Thanks for your help. I like the words yes, possible and some in the same sentence I suppose there is only way to find out. I can imagine from what you said about the soot and composition that it could vary quite a lot depending on the level of destruction from scene to scene.

I have been searching the forum today for images of an example where intensity could show some staining but no joy so far. Would you have any example images from non burnt surfaces with staining? I would be very grateful I am just trying to visualise what it may look like first

Best Wishes,
Scott

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Re: Arson investigators: intro to LiDAR class questions

Post by 3DForensics » Wed May 22, 2019 8:01 pm

Great discussion. Really appreciate you guys sharing this info.

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