Forensics Questions

john bellamy said:
I'm finding this thread fascinating!

I have a question too. In the case of a analysing a footprint ( not fingerprint ) what technique would be used? I have heard and seen various tecnhiques including filling up the the footprint with plaster.

Happy crime solving!

JB
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Well, depending on where it was left. If it was a smooth surface it can be lifted up like a fingerprint (with physical or chemical reactives) or even photographed with a proper scale and identification (and I think there's another electrostatic lifting technique... but I'm not sure how it works)

If it was a soft material like, for example, mud then it can be filled with plaster or even the silicone material the dentists use to make the molds for false teeth, as a result you obtain a more detailed impression...

hope it helps :)
 
IRL, what is the approximate time it takes to get results back from a DNA test (not paternity tests, just dna on skin/bone, etc)? There are some cases in the news that I'm just wondering if its normal to take that long to get results or if the authorities have results and are just keeping the info quiet for the time being.
 
GregNickRyanFan said:
IRL, what is the approximate time it takes to get results back from a DNA test (not paternity tests, just dna on skin/bone, etc)? There are some cases in the news that I'm just wondering if its normal to take that long to get results or if the authorities have results and are just keeping the info quiet for the time being.
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as far as I know, It can take several weeks, even a month... but it obviously depends on each case, cause the extraction of DNA from the sample is what takes most of the time (the actual identification technique can be done in an hour, give or take)

anyway, let me do some research so I can confirm it :)
 
I'm plotting out a crime novel centered around a private forensics lab and I was looking for new techniques in forensic facial approximation, using either the old-school markers on the skull or the digital projections.

Hope someone can help.
 
GregNickRyanFan said:
IRL, what is the approximate time it takes to get results back from a DNA test (not paternity tests, just dna on skin/bone, etc)? There are some cases in the news that I'm just wondering if its normal to take that long to get results or if the authorities have results and are just keeping the info quiet for the time being.
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It depends on what type of DNA test that's being run. The prep time in and of itself doesn't take THAT long. I've done labs where we did the prep of the sample early on in the lab via PCR (polymerase chain reaction)... and if I remember correctly (it's been years since I did it, and also it was only ever using short segments of DNA... so my estimations could VERY well be off). That portion only ever took between one to three hours. But that was just taking a small sample and making MANY copies of it. Which if you've got a large enough sample from skin/bone, may not be entirely necessary (but what amount would be considered to provide enough DNA, I don't know).

What I do remember took the longest was running the gels. I think that took a day or so. However, gel electrophoresis speed depends on both the quality of the gel and the strength of the electric field (I know another lab team ran their sample off the gel in a matter of minutes because they set up a weak gel with too strong a field). Also while gel electrophoresis produces the visual most are familiar with, I think in terms of a forensic investigation, they'd likely want something a bit more in depth.

So yeah, that probably doesn't REALLY answer your question... but hopefully gives you an idea of what kind of timing that might be involved?
 
Where do I find instructions on how best to use an electrostatic lifting apparatus. I have a scene in my novel where a crime scene analyst is explaining the process to a newbie of sorts.
 
LocardPrinciple said:
^Helps greatly, thanks.

What's the best way to collect technological evidence like a speaker and CPU?
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Well, first you'll have to collect all the biological samples (if any, for example, if there are blood stains on them), then dust them for prints (it's important not to skip this step, cause otherwise the prints will be missed) and put them on a properly sealed box... that would be the best way to collect them...
 
I have a question, regarding procedure. If for example at a crime scene there is more than one source of DNA (both hair and blood for example), do forensics test both ? Or do they test just one, the cheaper one, or the most accurate one ?
 
vraciul89 said:
I have a question, regarding procedure. If for example at a crime scene there is more than one source of DNA (both hair and blood for example), do forensics test both ? Or do they test just one, the cheaper one, or the most accurate one ?
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Both have to be tested... cause they may belong to different people (for example... the killer and an accomplice, or two killers, or one may be the victim's... and so... ;))
 
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