Crime Busters

In Crime Busters students will identify perpetrators of a certain crime by identifying unknown powders, liquids, and metals, and analyzing shoe prints, tire treads, paper chromatography, and fingerprints. Students should be able to use this data to answer some questions about who committed the crime and how the evidence supports their argument. This event was previously known as Science Crime Busters.

Supplies
Every team must bring a bunch of stuff in order just to get into the testing room. The team must have:


 * Lab aprons or coats. If lab aprons, make sure you're wearing long sleeves.
 * Also, make sure you have closed toe shoes, NO sandals
 * Indirect vent Goggles
 * Pencils (not pens, you will most likely make mistakes)

Also, the team should have the following:
 * Standard sheet of paper (both sides) with notes on anything involved with the event! Only one sheet of notes (typed or handwritten) is allowed per team.
 * Extra pencil for chromatography
 * Paper Towels
 * Magnet
 * Microscope Slides
 * Testing trays
 * pH paper
 * Wood Splints (Make sure you have extra)
 * Some form of scoop for the powders

The supervisor will provide everything else you need, so if you bring anything outside of what the rules allow you will be penalized.

Before the competition (at school practices)
Check with your SO coach to get the following materials to test:
 * Powders (Italics means it can be used in mixtures)
 * White Sand
 * Calcium Carbonate
 * Table Salt
 * Sugar
 * Flour
 * Cornstarch
 * Gypsum
 * Baking Soda
 * Powdered Gelatin
 * Powdered Alka-Seltzer
 * Sodium Acetate
 * Vitamin C
 * Yeast
 * Metals
 * Aluminum
 * Copper
 * Iron
 * Tin
 * Zinc
 * Magnesium
 * Liquids
 * Rubbing Alcohol
 * Household Ammonia
 * Water
 * Vinegar
 * Hydrogen Peroxide
 * Lemon Juice

The coach will also need-
 * a dropper bottle of 1M HCl (hydrochloric acid)
 * a dropper bottle of Iodine
 * pH or Litmus paper
 * 15-20 unknowns
 * 250 mL dH2O
 * chromatography materials (chromatography paper, ink to be tested, extra beaker for testing)

Make a chart for testing. For powders, include color, reactions with water, HCl, and Iodine; odor (distinct, faint, or none); shape (crystalline, granular, or powder), solubility (whether it dissolves in water or not), and reaction to pH or Litmus paper. For metals, include reactions to HCl and magnetic property (yes or no). For liquids, include smell, reactions to pH or litmus, and color. With your teammate, memorize the results (this is where two heads are better than one) and try testing unknowns made by the coach or other team members. If you can do this, it helps very much when it comes time for the competition.

Liquids
Each liquid has a "give-away", making them fairly easy to identify-
 * Lemon Juice has a strong lemon odor (and is a strong acid, like vinegar)
 * Ammonia is the only strong base
 * It is best to use pH paper first, before smelling the unknown liquid, so that you will never have to smell ammonia (even if by wafting) since it can be chosen conclusively if the unknown liquid has a very basic pH.
 * Vinegar has a distinctive vinegar odor (and is a strong acid, like lemon juice)
 * Rubbing Alcohol is neutral, but has a distinctive odor
 * Hydrogen Peroxide and water are very similar (both are odorless, neutral liquids), but there is a simple way to tell them apart. Fill a small well in your testing tray with the liquid, put in a few drops of iodine and stir. After about a minute (though sometimes more), tons of bubbles will appear if it is hydrogen peroxide, while nothing will happen in water (besides the color change due to iodine's color).

Metals
Almost every metal has a "give-away", making them fairly easy to identify-
 * Iron is the only magnetic metal
 * Copper is the only metal with a color other than grey (or similar).
 * Magnesium will often steam with HCl, and will also let off a strong odor when HCl is added.
 * Zinc will react vigorously (but will not steam) with HCl, and is non-magnetic.
 * Tin and aluminum are very similar (neither react very much with HCl), but there are a few things that can be done to tell them apart. First, tin often has a yellowish tint, which aluminum will never have. Next, tin is often fairly shiny, while aluminum is dull. Lastly, if the metal is very malleable, it is probably aluminum (think aluminum foil).

Chromatography
This is very easy to do but must be done with care. You put a dot of ink at one end of a strip of filter paper. Then, get a small cup of solvent (often dH2O) and put the paper on the cup just so that the ink dot is above the water line. Wait for the colors to separate and that's it! Once you have taken the paper out, quickly put a line in pencil where the top edge of the water is on the paper. This allows you to find the Rf (retention factor) value of any ink spot if they ask, ot they might be looking for it for full credit.

Fingerprints
Practice identifying and comparing fingerprints. There are 3 basic categories of fingerprints(arches, loops,and whorls). They are easily identified by there general shape and number of deltas (triangles made from ridges). Make sure you know if your event supervisor is looking for the basic type (loop, arch, whorl), or the more in-depth name (Tented Arch, Ulnar Loop, etc.).
 * Arches= a hill shape with no deltas
 * Tented arch= an arch with a sharp corner at the top point
 * Plain arch= an arch with a more rounded top point
 * Loops= a beanish shape with one delta
 * Ulnar Loop= A loop pointing towards the pinky
 * Radial Loop= A loop pointing towards the thumb
 * Whorls= a circle like shape with two deltas
 * There are many sub-categories of whorls, such as (but not limited to)-
 * Plain whorls (most important to know; sometimes simply referred to as "whorl")
 * Double loops
 * Accidental whorls
 * Tracings
 * It is highly unlikely that they will ask for one of these, so this should be the last thing you should worry about learning. However, the most important whorls to know are the plain whorl and double loop.

Polymers
You have to know PETE (1), HDPE (2), PVC (3), LDPE (4), PP (5),PS (6). HDPE, LDPE, and PP float in water while PETE, PVC, and PS do not. This means that the first group has a density less then one and the second group more then one.

''The following method of identifying the polymers is based on the assumption that the supervisor will only provide a beaker of water. A more precise method can be used if you are provided with corn oil, a certain percent concentrated solution of hydrogen peroxide, and a certain percent concentrated solution of salt water.''

Identifying the polymers in the first group is easy. HDPE and LDPE are translucent while PP is not. HDPE is relatively more translucent then LDPE. Identifying in the second group is also fairly simple. PS will SLOWLY drop down in water or half of the flecks will sink while the other will float. PVC is sometimes rubbery, but never transparent, while PETE is always clear.

Analysis
There are two common ways that an event supervisor could approach the analysis portion of the test-

Essay
By far the most common way that the analysis will be set up is in an essay form. They will likely give few instructions besides something along the lines of: "Based on your analysis of the evidence, who is likely the culprit?" However, there are many things that they may be looking for beyond just a name-

Rationale based on physical evidence- You must use the evidence to support your claim. Talk about every piece of physical evidence that points to that person. To connect someone to the crime scene, you would see a connection like "Joe works with flour daily, and flour was found at the crime scene" or even more simply "Joe's fingerprints were found at the crime scene".

Reasons why it wasn't the other suspects- Even if they do not explicitly ask for this, it is an excellent idea to include it in your essay. Write about a sentence for each person (more than a sentence if there is a lot evidence pointing towards them and you have to explain more in depth why it wasn't them). If there is a lot of evidence against a second person, but you're sure it wasn't them, then talk about a logical reason why there would be all of that evidence (for instance, "they work at the crime scene" is a common reason). Also, even if someone has no evidence against them, say that in your essay: "Joe had no evidence connecting him to the crime scene, so he was not the culprit".

Motives- Give a motive for the person you suspect to be the culprit, or if the proctor gave you possible motives in the bios, restate them. This can add a lot to your essay, and help support your claim even if you have the wrong person.

Multiple or No Culprits from List of Suspects- While most tests will have one culprit from the list of suspects, do not get trapped into thinking that it must be only one person. Some proctors may set up the test to point to two people working together, or they may leave insufficient evidence to point to anyone. If either is the case, adjust your essay structure to fit your claim and make a logical explanation. If correct, you will likely do very well. If incorrect, a logical explanation should get you a decent amount of credit for the essay anyway.

Essay Structure-This can never hurt to have, and takes very little time to do. A simple, yet effective structure goes as follows-


 * Intro Sentence- i.e. "Based on the evidence gathered, we concluded that the culprit was Joe".


 * Lead-in to evidence- i.e. "There is much evidence to support our conclusion"


 * State evidence in multiple sentences- i.e. "Flour was found at the crime scene, and Joe works with flour daily. Also, Joe's fingerprints and DNA were found at the crime scene. Finally, Joe.... etc."


 * Lead-in to other suspects- i.e. "In addition, there was not enough evidence to point to any of the other suspects"


 * Sentence on each suspect- See "Reasons why it wasn't the other suspects" section above


 * Conclusion Sentence- i.e. "Therefore, it can be concluded that Joe was the culprit."

Multiple Short Essays
With the time crunch often imposed on the scorers, a sequence of shorter essays (50 words or less) are asked addressing specific areas of analysis: something about the crime, how it was committed, who committed it, sequence of events, or something else of that sort.

At the Competition
Once you get your materials and the supervisor starts the competition, start by getting your chromatography paper started. Then, look at the test and see how long you think it will take or how much there is to do. If it is a lot, make sure you split up the work because you don't want to have wasted potential and then not finish. While the chromatography is going, identify all the unknowns using tests (see section above). Please note that at higher levels of the tournament (state, national) and even sometimes Regionals, different compounds may be combined with each other- for example, flour and Alka-Seltzer. While one person is testing unknowns, the other might want to do the fiber, hair, or polymer testing. If there is microscope set up for the hairs, make sure you go there first, because it will get crowded near the end, and you may have to waste time waiting. After all the unknowns are identified, read through your packet to learn about the crime scene and answer the questions. Then, after questions have been answered, write out the crime solution essay, discussing how the team chose the culprit(s), based on their motive and supporting evidence (the unknowns the person was carrying compared to the substances found at the crime scene). Following the supervisor's instructions, hand in your papers, clean up your lab area, and relax until the supervisor dismisses you.

'''Make sure to leave enough time for the essay. Depending on the event, it may be simple or extremely complex; the National supervisor for this year has a tendency to write events with complex essays that require a fair amount of time to write.'''

WARNING: The rules say you will get 50 minutes. However, the 50 includes the supervisor talking to you about safety/tips/rules/etc, so often you will only have 40-45 minutes to work. It is probably a good idea to practice with only 40-45 minutes to get used to competition conditions. At 2010 Nationals, a brief introduction was given, then 45 minutes to work, along with a 5 or 10 minute clean-up time after you had handed in your test.

HINT: In some competitions, you may not get full points for ONLY identifying the substance. In many instances, they will hand you a blank chart that you must fill your observations into. These observations may include (but are not limited to): HCl test reactions, Iodine test reactions, pH, Solubility in water, Shape, Size, or Color. Even though with one simple HCl and water test, you could figure out alka seltzer, taking time to test it or write down all observations could help you. Even if you skip a small portion, such as hairs, you can still place if you write down all the observations, and not just the identity of the substance, seeing as the identification and process of identifying the substance is worth 50% of your points. Some supervisors will even put a scoring chart on the front/back of the handout/packet that you are given to show you the breakup of points. Even if you fail to correctly identify a substance, the supervisor could give you partial credit for filling in observations.

Scoring
The scoring is composed of these elements:


 * Unknowns Identification (50% of total score) (Second Tiebreaker)


 * Chromatography (5%)


 * Polymer Testing/Natural and Man-Made Substances (Replaced Water Testing) (10%)


 * DNA, finger printing, tire treads, finger prints, shoe prints (10%)


 * Crime Solution Essay (25%) (First Tiebreaker)

Practice Tests
[[Media:SCB Test.pdf|"Dwisney Stars-Twenty Years Later" Test]]
 * Note: You will need to print off the fingerprints, shoeprints, and DNA yourself for the following tests.

[[Media:Answer Key.pdf|"Dwisney Stars-Twenty Years Later" Answer Key]]

[[Media:SCBtest3.pdf|2009 Northridge Invitational Test]]

[[Media:SCBanswers.pdf| 2009 Northridge Invitational Answers]]