Forensics C

[Jim_R]

Discussion for Forensics C

Forensics Wiki
2012 Tests for Forensics
2010 Thread
2011 Thread

[EASTstroudsburg13]

This event tends to be a trouble spot for our team. Are there any tips for practicing this event for people who have little to no prior experience with forensics?

[salcedam]

This event tends to be a trouble spot for our team. Are there any tips for practicing this event for people who have little to no prior experience with forensics?

What in particular seems to cause your team trouble? Specific parts of the tests (like powder testing and such) or more general-type problems like time management?

[EASTstroudsburg13]

I think it's that we have trouble studying what ends up on the tests, and that it's hard to get event experience before the competition. I think, last year, what was studied most was not on the test, so the people doing it did not really know what to do. I've never done it personally (though I may have to this year) so I don't know the particulars.

[salcedam]

What I would recommend is starting right off the bat with learning how to identify the powders since that's a major chunk of the test and subsequently, one of the more important parts of it. For powders, you should have some sort of flowchart in place so as you can sequentially go through different tests (such as solubility, flame colors, HCl reactions, etc.) until you can identify it. For example, to identify boric acid, the only test you need to do for that is to do a flame test because boric acid makes a green flame. LiCl gives off a red flame and KCl gives off a purple flame. Those are the only three powders that will give those distinctive colors. The others will either give you a yellow, orange-ish, or no flame color at all. That's when you need to continue with the next step which would be to determine solubility and so on and so forth. Then once you have powders down or at least have an idea of how to do them, move to the fibers and plastics and learning to identify those using burn tests (for the fibers in particular since they usually won't allow burn tests for plastics). For plastics, you identify them using densities so you need a flowchart just like for the powders of what to do when one plastic sinks in one solution. So let's say you have a plastic that sinks in water. You know that it must have a higher density so then you test the density using salt water. Different competitions will give different concentrations so you should know the densities of the various concentrations of salt water so that when they give you, let's say, a 10% salt solution and it sinks, you know that it must have a density higher than 1.074 g/mL since that's the density of a 10% salt solution. Then you should test the plastic using corn syrup or some high density liquid to see if it floats or sinks. If it sinks in corn syrup, it has to be PVC (according to the flowchart I've made) and if it floats, it's PETE. So basically, you need to research flowcharts on powders and plastics as well as learn specific characteristics of fibers such as how they react when burned and how they look. From powders, fibers, and plastics, you move on to everything else. I'd focus less on glass and dirt/tire tracks and such since that's mostly matching. Most tests that I've come across focus mainly on blood, fingerprints, reading mass spec, and the occasional entomology question. When studying those things, you don't need to get too in-depth, but you should go past the surface a little bit. I've had tests where they ask how fingerprints are formed, how many ridges a fingerprint has, things besides matching and identifying fingerprint types. Hope that helps somewhat!

[EASTstroudsburg13]

Wow, thanks! I might end up printing that post out as a reference. You should try putting some of that on the Forensics Wiki, I think it might be lacking in some of those areas.

[Phenylethylamine]

I think it's that we have trouble studying what ends up on the tests, and that it's hard to get event experience before the competition. I think, last year, what was studied most was not on the test, so the people doing it did not really know what to do. I've never done it personally (though I may have to this year) so I don't know the particulars.

It's incredibly helpful to have your team run through a full practice event. I know, it's complicated and requires a lot of materials, but try to set up a complete event – powders, fibers, whatever other evidence, relevant suspect info; you don't have to come up with it yourself, there are events available online for which you'd just have to find the necessary powders/fibers/stuff. Have them do the entire thing all at once, preferably with time constraints, but let them keep working if they run out of time (just change what color pen they're using or something so they can see how much they got done in the actual time).

Then, after seeing how they do on the complete event, you can give them more stations for the particular areas that they had trouble with (e.g., if they have problems with chromatography, give them a bunch of pens and different juices or whatever, and chromatography paper of various shapes and sizes, and make them do it over and over again until they're good at it).

[EASTstroudsburg13]

How much would that cost if we're starting from scratch? (Not saying we are, but just for reference) And are there any tests you would suggest? I don't want to go out and get a test that's not very good and base our materials on that.

[Phenylethylamine]

How much would that cost if we're starting from scratch? (Not saying we are, but just for reference) And are there any tests you would suggest? I don't want to go out and get a test that's not very good and base our materials on that.

You'd have some difficulty "starting from scratch" entirely – some of the powders are things that really only a chemistry teacher would have access to, so hopefully you at least have a friendly chemistry teacher handy. Nothing else should be terribly expensive, though: table salt and sugar (and maybe a couple other 'household' powders, I don't remember the list exactly), different types of plastic containers, various markers and/or pens. I have no idea how much chromatography paper costs, but I'd guess you can get large amounts of it for relatively low prices somewhere on the Internet. As for human, cat, and dog hair, you should be able to get those for free.

The Valley Forge Invitational test currently on the test exchange under Forensics looks pretty good as a starting point – it involves relatively few powder samples, but it's got quite detailed setup instructions.

To practice for powders separately, I'd suggest making a flow chart – giving specific tests to do, and then what step to take next based on the result – from tables or charts or other information that you find on the web, and then testing it practically by taking samples of two powders that should be differentiable based on a particular test and seeing if you can actually differentiate them.

[EASTstroudsburg13]

Okay, thanks for all the tips. We'll try them out and hopefully we can get a hang of this. I'll ask if we have any further questions after we start practicing.

[salcedam]

Good luck! And have fun! Forensics is a really fun event once you've got things down. And even then, it's still fun to be a CSI in a way.

[haverstall]

Yeah, I would say our preparation for Boyceville (which is next week) at this point for Forensics is nil, but a lot of it is just remembering stuff from previous years. I just did our first chromatography today for the heck of it, and I still love watching the colors separate.

Also, no matter how many times you do a flame test, it is still as awesome as the first time.

[salcedam]

Yeah, I would say our preparation for Boyceville (which is next week) at this point for Forensics is nil, but a lot of it is just remembering stuff from previous years. I just did our first chromatography today for the heck of it, and I still love watching the colors separate.

Also, no matter how many times you do a flame test, it is still as awesome as the first time.

Yo, haverstall...see you there! And Koko and Luo! PARTY TIME!

[haverstall]

Hopefully we'll do the same thing as last year and have an music party in our homeroom.

Back on forensics though, (this mainly pertains to salcedam) maybe my memory is bad, but weren't there an inordinate amount of things to ID at last year's Boyceville meet for Forensics? I recall somewhere around 8 powders and a ton of plastics.

[Kokonilly]

Yeah, I would say our preparation for Boyceville (which is next week) at this point for Forensics is nil, but a lot of it is just remembering stuff from previous years. I just did our first chromatography today for the heck of it, and I still love watching the colors separate.

Also, no matter how many times you do a flame test, it is still as awesome as the first time.

Yo, haverstall...see you there! And Koko and Luo! PARTY TIME!

Yeah, see you all there!

Oh, and I seem to be doing Forensics now at Boyceville. Looks like I'll just be recycling resources from last year... last-minute cancellations are never fun.