Wednesday, May 30, 2012

Techniques in Making Shoe Impressions



Topic
Crime scene investigators make shoe impressions with plaster of paris and dental stone.
Introduction
The most common method of entering and leaving an area where a crime is committed is by walking. Criminalists often gain information by examining the surfaces on which a perpetrator walked. Footwear or bare feet can leave superficial prints on firm surfaces such as flooring.
However, walking across a soft surface like damp soil leaves impressions or indentations.
Footwear impressions can provide crucial clues in an investigation. Prints or impressions can show the points of entry and exit at the crime scene.
In addition, shoes carry materials from one environment to another. This material can provide information about where this person has been.
An impression can tell a lot about the shoe that made it. Every shoe is unique, with its own pattern of wear and tear. Therefore an impression of footwear can be compared to a particular pair of shoes to help connect those shoes to the crime scene. Impressions can also tell something about the height and weight of the wearer. Heavy individuals make deeper impressions than light ones. In addition, a tall person has a longer stride than a short person.
There are several techniques for making casts of shoe impressions. In this experiment, you will compare the effectiveness of two materials in making casts: plaster of Paris and dental stone.
Time Required
45 minutes on day 1
45 minutes on day 2
Materials
a)      2 pounds (lbs)(0.91 kilograms [kg]) of dental stone in a large
b)      Ziploc™ bag
c)      3 lbs (1.36 kg) of plaster of paris in a large ziplock bag
d)      3 to 5 cups of water in a bottle
e)      5 to 10 twigs or craft (Popsicle™) sticks soaked in water
f)        3 or 4 long strips of cardboard (about 4 inches [in.] by 24 in.
g)      [10.2 centimeters (cm) by 61 cm])
h)      large spoon
i)        talcum powder
j)        magnifying glass
k)      scrub brush
l)        paper towels
m)    access to water
n)      science notebook
Procedure, Day 1
  1.   Follow your teacher to an outdoor area where there are some shoe impressions.
  2.   Closely examine two footprints. Carefully remove any rocks, twigs, or other debris from the footprints.
3.   Sprinkle a little talcum powder over these two footprints to help hold the soil in place and secure the impressions.
  4.   Build a retaining wall around each impression using strips of cardboard (see Figure 1). 
(This wall will prevent the plaster of paris or dental stone from escaping when it is poured into the impression.)
  5.   Make a cast of one footprint using dental stone. To do so:
 a. Pour about 1 cup of water into the Ziploc™ bag of dental stone.
b. Knead the bag of dental stone for 2 to 3 minutes (min) to mix thoroughly.
c. Examine the consistency of the dental stone. Ideally, it should be similar to pancake batter. If it is too thick, add a little more water. (Be careful; if you add too much water, your mixture will be too thin.)
d. The dental stone becomes firm very quickly, so work rapidly to pour the mixture. Avoid pouring the material directly into the impression, which can distort it. Instead, hold the spoon just above the impression and slowly pour the mixture into the spoon so that it falls into the impression. When the impression is about half full, remove the spoon and pour the remaining mixture directly. The poured cast should be 2 to 3 in. (about 5 to 7.5 cm) thick.
e. Use a stick or pencil to etch your name and the date in the upper surface of dental stone.
f.   Let the cast sit for 30 min to harden. During this time, carry out step 6 below.
g. After 30 min or more, insert the handle of the spoon into the ground about 1/2 in. (1.2 cm) from the impression and gently pry up the cast.
h. The cast may have soil or grass on it; do not remove it at this time.
i.   Take the cast indoors and allow it to harden for 24 hours.
6.   Make a cast of the other shoe impression using plaster of paris. To do so:
a. Pour about 1 cup of water into the Ziploc™ bag of plaster of paris.
b. Knead the bag of plaster of paris and water for 2 to 3 min to mix thoroughly.
c. Examine the consistency of the mixture. Ideally, it should be similar to pancake batter. If it is too thick, add a little more water. (Be careful; if you add too much water, your mixture will be too thin.)
d. Pour about 1/2 in. (1.2 cm) of plaster of paris into the impression, using the spoon as you did earlier to avoid damaging the impression. Add some reinforcing materials such as twigs or craft (Popsicle™) sticks that have been soaked in water (see Figure 2). (Dry sticks will absorb water from the plaster of paris and make it brittle.) Quickly finish pouring the plaster of paris into the impression to a thickness of at least 3 in.
e. Follow directions e through i in step 5.
Procedure, Day 2
  1.   Examine each shoe cast. In your science notebook, note any significant differences in the casts.
  2.   Using a scrub brush, gently clean each cast with water. Pat dry each cast with paper towels.
  3.   Examine each shoe cast again. In your notebook, note whether or not washing damaged either cast.
4.   Closely examine each shoe cast with a magnifying glass. Search for nicks, cuts, or scrapes in the casts that indicate identifying markings on the shoes. Record these in your science notebook.
Analysis
  1.   Why might an investigator make casts of shoe impressions?
  2.   in your opinion, which cast was easier to pour, the dental stone or plaster of paris? Explain your answer.
  3.   Which material held up best to washing? Explain your answer.
  4.   Which material provided the most detail when viewed under the magnifying glass? Explain your answer.
  5.   Describe any nicks, scratches, wear patterns, or other unique marks found in either cast.
  6.   What information might a forensic investigator acquire from examining a shoe cast?
  7.   Complete a Venn diagram (see Figure 3) comparing the two casting materials.

19 comments:

  1. Howdy! Would you mind if I share your blog with my twitter group?

    There's a lot of people that I think would really enjoy your content. Please let me know. Many thanks

    My website ... Visit Link

    ReplyDelete
  2. Very good blog! Do you have any recommendations for aspiring
    writers? I'm planning to start my own website soon but I'm a little lost on everything.
    Would you advise starting with a free platform like Wordpress or go for a paid option?
    There are so many choices out there that I'm completely confused .. Any ideas? Thank you!

    My homepage ... know more

    ReplyDelete
  3. I believe what you published made a ton of sense.

    But, think on this, what if you added a little content?
    I mean, I don't want to tell you how to run your blog, but suppose you added something that grabbed people's attention?
    I mean "Techniques in Making Shoe Impressions" is a little boring.

    You should peek at Yahoo's front page and watch how they write news headlines to grab people interested. You might try adding a video or a related picture or two to grab readers excited about everything've got to say.
    In my opinion, it could bring your posts a little bit more
    interesting.

    my site more info

    ReplyDelete
  4. I believe what you published made a ton of sense. But, think on this, what if you added a little content?
    I mean, I don't want to tell you how to run your blog, but suppose you added something that grabbed people's attention?

    I mean "Techniques in Making Shoe Impressions" is a little boring.
    You should peek at Yahoo's front page and watch how they write news headlines to grab people interested. You might try adding a video or a related picture or two to grab readers excited about everything've got to say.
    In my opinion, it could bring your posts a little
    bit more interesting.

    Also visit my web site more info

    ReplyDelete
  5. I'm not sure why but this web site is loading extremely slow for me. Is anyone else having this issue or is it a issue on my end? I'll
    check back later on and see if the problem
    still exists.

    ReplyDelete
  6. Have you ever considered about including a little bit more than just your articles?
    I mean, what you say is valuable and everything.

    However think about if you added some great visuals or videos to give your posts more,
    "pop"! Your content is excellent but with pics and video clips, this site could undeniably be one of the best
    in its niche. Great blog!

    my web page :: recruitment agencies Johannesburg

    ReplyDelete
  7. Unquestіonablу belіeve that which
    you saіd. Your fаvoгіte justіficаtion seеmed to be оn the nеt the
    simpleѕt thing to be awагe of. I say to you, I сertainly get irked while pеople think about worriеs thаt they рlaіnlу dоn't know about. You managed to hit the nail upon the top and defined out the whole thing without having side-effects , people could take a signal. Will probably be back to get more. Thanks

    My web page ... http://rechockey.net/profile/kaitlyng89

    ReplyDelete
  8. Woah! I'm really digging the template/theme of this website. It's simple, yet effective.
    A lot of times it's very difficult to get that "perfect balance" between usability and appearance. I must say that you've done a awesome job with this.
    In addition, the blog loads extremely quick for me on Firefox.
    Excellent Blog!

    my site; http://75.102.23.84/user/view/profile/login/rubendenn

    ReplyDelete
  9. excellent issues altogether, you simply won a
    new reader. What may you suggest about your put up that you just made a few days ago?
    Any positive?

    my homepage; Saphire Ecig Review

    ReplyDelete
  10. Good day! Do you use Twitter? I'd like to follow you if that would be ok. I'm undoubtedly enjoying your blog and look forward to new updates.


    Feel free to surf to my blog post; Test Force Extreme

    ReplyDelete
  11. Write more, thats all I have to say. Literally, it seems as though you relied on the video to make your point.
    You obviously know what youre talking about, why waste your intelligence on just posting videos to your blog when you could be giving us something enlightening to read?

    Here is my web blog ... RX Rejuvenex

    ReplyDelete
  12. If you are going for most excellent contents like myself, just pay a quick
    visit this web page everyday as it presents feature contents, thanks

    My homepage ... Building Muscle

    ReplyDelete
  13. Good blog! I really love how it is easy on my eyes and the data are well written.

    I am wondering how I might be notified whenever a new post has been made.
    I have subscribed to your feed which must do the trick!
    Have a nice day!

    Take a look at my blog Click the following website

    ReplyDelete
  14. Appreciating the dedication you put into your blog and
    detailed information you offer. It's great to come across a blog every once in a while that isn't the same outdated rehashed material.
    Fantastic read! I've bookmarked your site and I'm adding your RSS feeds to my Google account.


    Feel free to visit my webpage :: moving company los angeles

    ReplyDelete
  15. They can be used in numerous ways to assist
    your young puppy in learning where the proper place to go to the bathroom is.

    From house training to tricks, lots of great basic info is shared here.
    Be fair and understanding when disciplining your pet.

    When you are both comfortable with the basics, you might want to teach your new friend some tricks.
    Adopting dogs during stressful times such as
    the holidays or personal stress is never a good idea.


    Here is my blog: motapuppies

    ReplyDelete
  16. The fіnal person residing in the circle wins the oѵerаll game.
    Thiѕ reρeаts until onе tеam fills theiг large bucket
    fiгst fοr the wіn. )How many steрs per minutе does an averagе toddler taκе.
    Εnsure to instгuсt thе сompany to
    weaг οld clotheѕ anԁ brіng а сhange of thoroughly clean сlothѕ wіth.
    So you bеtter fіnd other plaуerѕ avаilablе online рlaying this game.


    Ηere is mу site free online fun math games

    ReplyDelete
  17. I loved as much as you'll receive carried out right here. The sketch is attractive, your authored material stylish. nonetheless, you command get bought an shakiness over that you wish be delivering the following. unwell unquestionably come further formerly again since exactly the same nearly very often inside case you shield this increase.

    Look at my blog post garage doors in phoenix

    ReplyDelete
  18. Hello it's me, I am also visiting this web site daily, this web page is truly nice and the visitors are in fact sharing pleasant thoughts.

    my web-site; seo sem training

    ReplyDelete
  19. I couod not resist commenting. Well written!

    Here is my page: battlefield 4 Cheats pc download

    ReplyDelete