Case Notes - Trace Evidence Exam-1

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Pennsylvania State University *

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401W

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Chemistry

Date

Apr 3, 2024

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docx

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Uploaded by MasterIceGiraffe34

P ENN S TATE U NIVERSITY C RIME L AB 1313 Shaler Way University Park, PA 16802 Case Number: PSUCL-01 Criminalist: Joseph Taggart Date: 20-FEB-2024 Trace Evidence Examination On 20-FEB-2024 at 937 , I received the following items of evidence for examination: Item Item Description 8 Broken glass from bedroom floor under window 13(c1) Lisa bathrobe: glass chips 19 Towel from kitchen sink 23(b1 ) Richard left shoe: light yellow powder 30(a) Two blue-colored paint chips removed from skull of Richard S. 45(d2 ) Ralph shoes: light yellow powder 50 Dented window frame 54 Blue crowbar, Richard’s garage Items 23(b1) and 45(d2): The powder from Richard’s left shoe and from Ralph’s shoes appear to be similar when examined with the stereo light microscope (SLM). An initial analysis with the FT-IR didn’t provide a known chemical identity of the powder, so a series of tests will be performed to narrow down the identity of the substance by identifying its components. The first test is a microcrystal test to test for the presence of either ammonium or potassium ions. Procedure for microcrystal test – hydrochloric acid and platinic chloride test for ammonium or potassium ions: 1) Place three particles of unknown powder onto a microscope slide 2) Add a single small droplet of dilute hydrochloric acid to dissolve the particles into solution 3) Next to the droplet of dissolved unknown, place a small single droplet of platinic chloride 4) Using a sharp toothpick draw the two droplets together and then place under the microscope 5) View the area where the two drops meet at 100 times magnification a. If the test is positive, crystals will form where the drops meet on the slide. The crystals will be yellow in color and octahedral in shape. Results of microcrystal test Item Color Change Crystal Shape Positive or Negative 23(b1) – Richard left shoe: light yellow powder yellow octahedra + 45(d2) – Ralph shoes: light yellow powder yellow octahedra + To narrow down whether the ion present is ammonium or potassium, we will use a hanging drop test. If there is ammonium present, it will interact with the sodium hydroxide to produce ammonia gas, which will rise up and mix with the hanging drop of platinic chloride and generate the yellow crystals. If the ion Initials: JT Date: 20-FEB-2024 Page 1 of 5 FRNSC 100 – F22

P ENN S TATE U NIVERSITY C RIME L AB 1313 Shaler Way University Park, PA 16802 present is potassium, the hanging drop test result will be negative, as no potassium gas is produced so no yellow crystals will form. The hanging drop test will be performed to show whether the reaction is caused by the ammonium or potassium ions. *Pay attention as you read through this. This is NOT the same procedure as the paragraph above. If you repeat what you have for the previous test, it’s going to be wrong. You are using a lot of the same technique and the same reagents, but the introduction of a new one changes the test method slightly.* Procedure for hanging drop test – sodium hydroxide and platinic chloride test for ammonia gas: 1) Place three particles of unknown powder into the depression of a well slide 2) Add a single small droplet of platinic chloride to dissolve the particles into solution 3) On a separate coverslip, place a single drop of sodium hydroxide 4) Invert the coverslip, and then place the coverslip – drop-side down – over the well so that any vapors from the sample can interact with the reagent in the hanging drop. 5) View the drop on the coverslip under the microscope to look for crystals a. If the test is positive, crystals will form in the drop hanging from the coverslip. The crystals will be yellow in color and octahedral in shape. Results of hanging drop test Item Color Change Crystal Shape Positive or Negative 23(b1) – Richard left shoe: light yellow powder yellow octahedra + 45(d2) – Ralph shoes: light yellow powder yellow octahedra + After narrowing our IR spectra search for compounds that contain ammonium as part of their molecular structure, the FT-IR exam is run again. With the narrowed parameters, the FT-IR finds a match. The powder from both items 23(b1) and 45(d2) is identified as ammonium phosphate. After a search of the internet for uses of the identified powder, the case detective has been called to return to the scene to search for a fire extinguisher. If the item is found at the scene, it will be swabbed and any powder on the item compared to the evidence items 23(b1) and 45(d2). Items 54 – Blue crowbar: An examination of the crowbar with the SLM reveals a metallic gray smudge approx. 4 inches from the curved end of the crowbar. A tape lift was done of the smudge: some metallic gray flakes and dull white granules are visible on the tape. The items from the tape lift were sub-itemized as follows: Item Item Description Initials: JT Date: 20-FEB-2024 Page 2 of 5 FRNSC 100 – F22

P ENN S TATE U NIVERSITY C RIME L AB 1313 Shaler Way University Park, PA 16802 54(a) Blue paint chip exemplars from crowbar 54(b) Dull white granules from crowbar smudge 54(c) Metallic gray flakes from crowbar smudge Item 54(a) – blue paint chip exemplars: Stereo light microscope examination: Examination of item 54(a) – paint chips from the crowbar were compared with item 30(a) - two blue- colored paint chips removed from skull of Richard S. When compared side by side, the paint chips appear to be the same shade of blue. Scanning electron microscope (SEM) exam: The SEM exam reveals that the paint samples in item 54(a) and 30(a) both contain the following elements: - Iron - Silicon - Magnesium The exemplar paint chips from the crowbar and the evidence chips removed from Richard’s skull are chemically indistinguishable – the analysis with the SEM shows them to contain the same elements – therefore, we cannot out the crowbar as the source of the paint chips in Richard’s skull. The paint chips from the skull and the paint chips from the crowbar are a probable match. Item 54(b) – dull white granules: Polarized light microscopy (PLM) exam of dull white item 54(b) granules/powder: A few of the particles were removed from the tape lift and placed on a microscope slide. The particles appear dark under crossed polars, indicating the powder is isotropic, meaning it is unable to influence polarized light. In plane polarized light, the particles appear to have conchoidal fractures, which are a common feature of broken glass. Using the immersion method, glass from the crowbar and item 8 - broken glass from bedroom floor under window were compared. The glass from the crowbar and the glass from the broken window are similar in refractive index (RI), therefore the glass from the window cannot be excluded as a source of the glass found on the crowbar. It is likely that the glass on the crowbar came from the bedroom window. The glass in item 8 was also compared with item 13(c1) - Lisa bathrobe: glass chips. Using the immersion method, the glass from the robe and the glass from the broken window are found to be similar in refractive index (RI), therefore the glass from the window cannot be excluded as a source of the glass found on the robe. It is likely that the glass on the bathrobe came from the bedroom window. Item 54(c) – metallic gray flakes: Scanning electron microscope (SEM) exam of item 54(c) metallic gray flakes: The examination of the metallic flakes with the SEM identify the substance as aluminum. Initials: JT Date: 20-FEB-2024 Page 3 of 5 FRNSC 100 – F22

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