Forensics C

[bandgeek165]

So it's my first year doing Science Olympiad and I got this event only to find out that there was no information from prior years (oh joy!). I was just wondering if anyone could possibly give me an idea of how in depth to study the fingerprint analysis stuff and how in depth you have to go with the spatters. Thanks!!!

[Dragonshark]

So it's my first year doing Science Olympiad and I got this event only to find out that there was no information from prior years (oh joy!). I was just wondering if anyone could possibly give me an idea of how in depth to study the fingerprint analysis stuff and how in depth you have to go with the spatters. Thanks!!!

I'd primarily focus on qualitative analysis (white powders) and polymers (hairs, fibers, plastics), since they are worth a significant portion of the event, and require a lot of experience and practice in order to do well on them.

Fingerprints are pretty much guaranteed to be included. I would know the basic classification systems (arches, loops, whorls), including more specific patterns (ex. tented arches, double loops, etc.), since you'll be asked to match the print(s) at the crime scene to the suspect prints, if there are any matches. Another thing that you'll probably be familiar with are common fingerprint detection techniques (dusting, ioding fuming, ninhydrin, cyanoacrylate fuming). You should know with what substances/molecules each of the techniques target and which are most appropriate for a particular surface.

Blood spatters may also be included, though it's not as common as fingerprints. You should know the formulas for angle of impact (AOI = arcsin(width of droplet / length of droplet)) and point of origin (PO = tan(AOI) * (distance from center of stain to point of convergence)). You should also know how to determine the area of convergence for a spatter, though that's very easy to do - just draw a line from each droplet and circle the area where the lines intercept. You may also be asked to determine the velocity of a drop. I don't have an exact formula for this, but know that droplets that hit a surface at a higher velocity will appear smaller afterwards.

There's plenty of tests at the Test Exchange. Look at previous years for more tests; they should be essentially the same as this year's, except I don't think you have to worry about gas chromatography and water testing. You should also check the Wiki for more notes, especially on qualitative analysis. There are also a bunch of useful links here.

[Phenylethylamine]

So it's my first year doing Science Olympiad and I got this event only to find out that there was no information from prior years (oh joy!). I was just wondering if anyone could possibly give me an idea of how in depth to study the fingerprint analysis stuff and how in depth you have to go with the spatters. Thanks!!!

I'd primarily focus on qualitative analysis (white powders)[...]

Two words: flow chart. Find one on the internet, make one, whatever, but have one on your notes sheet and get familiar with using it.

[bandgeek165]

So it's my first year doing Science Olympiad and I got this event only to find out that there was no information from prior years (oh joy!). I was just wondering if anyone could possibly give me an idea of how in depth to study the fingerprint analysis stuff and how in depth you have to go with the spatters. Thanks!!!

I'd primarily focus on qualitative analysis (white powders) and polymers (hairs, fibers, plastics), since they are worth a significant portion of the event, and require a lot of experience and practice in order to do well on them.

Fingerprints are pretty much guaranteed to be included. I would know the basic classification systems (arches, loops, whorls), including more specific patterns (ex. tented arches, double loops, etc.), since you'll be asked to match the print(s) at the crime scene to the suspect prints, if there are any matches. Another thing that you'll probably be familiar with are common fingerprint detection techniques (dusting, ioding fuming, ninhydrin, cyanoacrylate fuming). You should know with what substances/molecules each of the techniques target and which are most appropriate for a particular surface.

Blood spatters may also be included, though it's not as common as fingerprints. You should know the formulas for angle of impact (AOI = arcsin(width of droplet / length of droplet)) and point of origin (PO = tan(AOI) * (distance from center of stain to point of convergence)). You should also know how to determine the area of convergence for a spatter, though that's very easy to do - just draw a line from each droplet and circle the area where the lines intercept. You may also be asked to determine the velocity of a drop. I don't have an exact formula for this, but know that droplets that hit a surface at a higher velocity will appear smaller afterwards.

There's plenty of tests at the Test Exchange. Look at previous years for more tests; they should be essentially the same as this year's, except I don't think you have to worry about gas chromatography and water testing. You should also check the Wiki for more notes, especially on qualitative analysis. There are also a bunch of useful links here.

Thank you so much!!! I have the polymers covered for sure and I'm working on perfecting my identification of powders. The spatter stuff is new to me though so the formulas are greatly appreciated! Fingerprints are going to be a lot to research, but other than that I think i'm good. Hopefully I'll be able to pull all of it together in time. Thanks again!!!!!!!!!

[bandgeek165]

So it's my first year doing Science Olympiad and I got this event only to find out that there was no information from prior years (oh joy!). I was just wondering if anyone could possibly give me an idea of how in depth to study the fingerprint analysis stuff and how in depth you have to go with the spatters. Thanks!!!

I'd primarily focus on qualitative analysis (white powders)[...]

Two words: flow chart. Find one on the internet, make one, whatever, but have one on your notes sheet and get familiar with using it.

Ok do you know of any good sites with flow charts? I have a chart, but it's rather basic and I'm unable to make my own because my lovely AP Chem teacher in charge of the chemicals never got back to me about doing the experiments. I've gotta give you guys who have been doing this event credit, it's a lot more work than I thought it was going to be.

[salcedam]

Ok do you know of any good sites with flow charts? I have a chart, but it's rather basic and I'm unable to make my own because my lovely AP Chem teacher in charge of the chemicals never got back to me about doing the experiments. I've gotta give you guys who have been doing this event credit, it's a lot more work than I thought it was going to be.

Try going to the link that Dragonshark posted at the end that's linked to the soinc.org Forensics site. I believe there are a few dichotomous keys posted up there. ^.^

[haverstall]

Ok do you know of any good sites with flow charts? I have a chart, but it's rather basic and I'm unable to make my own because my lovely AP Chem teacher in charge of the chemicals never got back to me about doing the experiments. I've gotta give you guys who have been doing this event credit, it's a lot more work than I thought it was going to be.

Try going to the link that Dragonshark posted at the end that's linked to the soinc.org Forensics site. I believe there are a few dichotomous keys posted up there. ^.^

Also, I would suggest that you practice with that key at least once before your competition. Going into a competition w/o practicing your key is like not having a key at all. You won't be familiar with it, and while it does seem easy, there are always things that can trip you up.

[bandgeek165]

Ok do you know of any good sites with flow charts? I have a chart, but it's rather basic and I'm unable to make my own because my lovely AP Chem teacher in charge of the chemicals never got back to me about doing the experiments. I've gotta give you guys who have been doing this event credit, it's a lot more work than I thought it was going to be.

Try going to the link that Dragonshark posted at the end that's linked to the soinc.org Forensics site. I believe there are a few dichotomous keys posted up there. ^.^

Took me a while to find it, but I found one that looks usable. I'll try to test it out if I can get the powders, but the way things are going I might need to improve. Anyways thanks so much for the help!!!!! This is gonna be an interesting event... xD

[Phenylethylamine]

Ok do you know of any good sites with flow charts? I have a chart, but it's rather basic and I'm unable to make my own because my lovely AP Chem teacher in charge of the chemicals never got back to me about doing the experiments. I've gotta give you guys who have been doing this event credit, it's a lot more work than I thought it was going to be.

Try going to the link that Dragonshark posted at the end that's linked to the soinc.org Forensics site. I believe there are a few dichotomous keys posted up there. ^.^

Also, I would suggest that you practice with that key at least once before your competition. Going into a competition w/o practicing your key is like not having a key at all. You won't be familiar with it, and while it does seem easy, there are always things that can trip you up.

True: if the key says to add a particular reagent and look for a precipitate, or bubbles, or a color change, you'll be much more successful at identifying it if you know in advance what that precipitate looks like, or how much the thing will bubble, or what shade the color will change to.

For example, at one time I was using a flow chart essentially unmodified off the Internet, and one difference relied on the smell produced by adding a reagent to a particular powder. I have a terrible sense of smell, and often couldn't tell whether the mixture smelled like anything, which made that method less than ideal for me. I've since learned to identify the odor, but it did take practice.

[jkting3]

For paper chromatography, do you calculate the Rf values using the middle of the pigment smudge/blob or do you calculate it using the top of the pigment line? I looked online and I know both are used. For Tiger, I used the top of the pigment and lost points for being not exact since the event supervisor made the answer key using the middle. Is there any preference to the top or the middle?