Chris_Halkides
Penultimate Amazing
- Joined
- Dec 8, 2009
- Messages
- 12,578
how the luminol was applied might be a factor
Here is a bit more on overspray (scroll down the link about halfway):
"As noted above, Luminol can in fact react with around 100 other substances and can also appear to give a positive response when it is not reacting with anything -it can “auto- luminesce”. Sometimes the scientist will add some extra spray (what the witness referred to as “overspray”) in order to enhance the quality of the glow so that it will show up in a photograph.
In speaking of a photograph of the dinghy (see above) the scientist said that “this run down here” which appears as the fluorescent streak on the photograph, is just the chemical itself running down towards the back. (651) Like “overspray” the accumulation of the Luminol is “auto-luminescing”.
The witness says, “The glow is very pale to some extent, even though I’m calling it strong and weak.” (651) It is hard to know what this means. The witness explains more about her methods when she says:
Even when it’s strong it’s not particularly bright so, we spray multiple times to enable it to come out in a photograph so that’s why there has been some overspray of the chemical which has then run down towards the back and pooled at the back. (652)
So, the desire to get a good photograph, requires repeated applications of the Luminol, which can then “auto luminesce” as appears to be the case in the above photograph.
However, as explained above, the witness claimed to be able to distinguish between such “false positive” appearances and “true positive” appearances on the basis of her experience and by the sparkle, glow, colour and longevity of the response."
I am not yet convinced that the over application of luminol must have led to auto luminescence and thus to the results seen in this case. However, the over application might still be playing a role in the results, even if it is not the sole reason for them.
EDT
Here is a little bit more on auto luminescence. James O. Pex wrote, "Luminol, once used, will oxidize when dry and cause autoluminesence when the area is re-sprayed at a later date."
Here is a bit more on overspray (scroll down the link about halfway):
"As noted above, Luminol can in fact react with around 100 other substances and can also appear to give a positive response when it is not reacting with anything -it can “auto- luminesce”. Sometimes the scientist will add some extra spray (what the witness referred to as “overspray”) in order to enhance the quality of the glow so that it will show up in a photograph.
In speaking of a photograph of the dinghy (see above) the scientist said that “this run down here” which appears as the fluorescent streak on the photograph, is just the chemical itself running down towards the back. (651) Like “overspray” the accumulation of the Luminol is “auto-luminescing”.
The witness says, “The glow is very pale to some extent, even though I’m calling it strong and weak.” (651) It is hard to know what this means. The witness explains more about her methods when she says:
Even when it’s strong it’s not particularly bright so, we spray multiple times to enable it to come out in a photograph so that’s why there has been some overspray of the chemical which has then run down towards the back and pooled at the back. (652)
So, the desire to get a good photograph, requires repeated applications of the Luminol, which can then “auto luminesce” as appears to be the case in the above photograph.
However, as explained above, the witness claimed to be able to distinguish between such “false positive” appearances and “true positive” appearances on the basis of her experience and by the sparkle, glow, colour and longevity of the response."
I am not yet convinced that the over application of luminol must have led to auto luminescence and thus to the results seen in this case. However, the over application might still be playing a role in the results, even if it is not the sole reason for them.
EDT
Here is a little bit more on auto luminescence. James O. Pex wrote, "Luminol, once used, will oxidize when dry and cause autoluminesence when the area is re-sprayed at a later date."
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