Forensics C

[pikachu4919]

...I have a wiki page. I think the answer is there. Plus, Princeton has their ES's photos on their website. The guy in the blue lab coat was the EHS representative watching over the chem events.

[scioly2012]

What are the components of a good analysis? I always seem to lose the most points on that section, which isn't good because it's 30% of our score... Pls help SOS

[pikachu4919]

What are the components of a good analysis? I always seem to lose the most points on that section, which isn't good because it's 30% of our score... Pls help SOS

When I write my forensics tests, I do reserve a chunk of the points for listing out what you found, but it's far from being the biggest piece of the pie. I set aside the majority of the points on the analysis essay on my tests to be for connections between the evidence and actually figuring out the crime.

It IS important to list out what you found/identified, because otherwise, you wouldn't be able to know 'whodunit.' However, perhaps, the most important thing to do when writing a good analysis is to be able to connect what you found/identified to who you think is guilty, plus, what reasons you think the most likely culprit may have for committing the crime that they allegedly did.

Being able to do all the trace ID's is one part. Being able to take all of that, put it together, and piece together who most likely committed the crime based on what you found is another. Ultimately, the goal IS, after all, to 'solve' a crime scene (solve in quotes bc irl you'd still need to question them further, run more tests on the evidence you find, and try them in court, but my point still stands), not to just play a giant game of match/no-match, and those connections between traces and suspects are what good analyses *should* look for. (*should* because not every supervisor may do that)

[BatAtForennsiccs]

How is this event actually structured? We were under the impression there would be a multiple choice and lab section at regionals, but it was just a paper chromatography lab. Will there always be paper chromatography, and what other sorts of tasks can we expect at states?

[pikachu4919]

How is this event actually structured? We were under the impression there would be a multiple choice and lab section at regionals, but it was just a paper chromatography lab. Will there always be paper chromatography, and what other sorts of tasks can we expect at states?

Huh, that’s weird that you only got a paper chromatography lab. In reality, there are five total parts, including that, which the rules elaborate more on (albeit with typos this year but they haven’t changed much at all in 7 years). If your state supervisor does a good job running the event, you should get lab portions for all the rest of the parts (powders, polymers, chromatography/mass spec, physical evidence), ‘technically’ excluding the analysis, which is always written.

[YungMihi]

Hey anyone have any good resources for soil id, pollen, and ento? These topics haven't really come up in the states or regionals tests but I feel like they will at Nats.

[ET2020]

Can someone please clarify what concentrations of liquids will be used? The rules just say "10% NaCl, 46% isopropyl alcohol" etc without specifying whether it is percent by mass or volume. Also many of the old nationals test provide solution concentration and density, but their numbers don't make sense to me. For example one test says "46% isopropyl alcohol: 0.95 g/cm^3). The problem is that 46% iso by mass has a density of 0.88, while by volume has a density of 0.90. Does anybody know if we can get clarification on this?

[pikachu4919]

Hey anyone have any good resources for soil id, pollen, and ento? These topics haven't really come up in the states or regionals tests but I feel like they will at Nats.

The wiki is a good start, and so is this (it's the national supervisor's website). From there, you could expand your own search, as that's a much more effective way to learn.

Can someone please clarify what concentrations of liquids will be used? The rules just say "10% NaCl, 46% isopropyl alcohol" etc without specifying whether it is percent by mass or volume. Also many of the old nationals test provide solution concentration and density, but their numbers don't make sense to me. For example one test says "46% isopropyl alcohol: 0.95 g/cm^3). The problem is that 46% iso by mass has a density of 0.88, while by volume has a density of 0.90. Does anybody know if we can get clarification on this?

The recipes for those solutions are actually found here, and having used this before, I know for sure that it is not percent by mass lol. I'm not sure what system that's based on, but it is literally the national supervisor's recipes, so doesn't hurt to follow it, I guess.

[potatosoup9000]

Does anyone know how Snell's law/index of refraction calculations were done at nationals? The seniors from our team never did them. Were they done normally, like shinning a laser through a flat sample, or do you have to do extra math for the spherical shape of the sample?
Thanks!

[sofossils]

Hello all! I am looking for a "portable" replacement to a Bunsen burner for flame tests. Does anyone have any suggestions for something that I could buy for my team? We do not have access to a chemistry lab on a regular basis, and using matches/candles did not work well! Any advice is welcome.