Course Forensic Science Unit VII Paint Essential Question How can paint chips be observed, compared, and used to prove ownership?

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1 Course Forensic Science Unit VII Paint Essential Question How can paint chips be observed, compared, and used to prove ownership? TEKS (c) (1)(A)(B) (2)(F)(G)(H) (3)(A)(D)(E)(F) (5)(C)(E J) (6)(A D)(G)(H) (7)(A) Prior Student Learning Compounds/ elements Solutes and solvents How paint is considered a basic compound Estimated Time 4 hours total 45 min. lecture 45 min. Paint Activity Day 1 30 min. Paint Activity Day 2 30 min. Review Puzzle 30 min. Quiz Forensic Paint Analysis Rationale A black car is not always just a black car. When black paint from several different vehicles is compared, it can sometimes look as though they are all the same. If a person wanted to cover a small scratch or ding, any black paint might do. However, when the situation is more serious, such as a hit-and-run, forensic science can be used to analyze the paint and tell different shades of black from each other to solve crimes. Objectives The student will be able to: 1. Identify the different components of automobile paint. 2. Characterize the microscopic examination of paint. 3. List and define the techniques used in paint comparisons. 4. Understand how to properly collect and preserve paint evidence. Engage Use the following story and questions for a class discussion. Use the Discussion Rubric for assessment. How was the bicycle (pink paint) a key piece of evidence in this case? Could it have been any pink bike? What other factors linked investigators to the suspect? Key Points I. Comparison of Paint A. Paint is composed of a binder and pigments, and other additives that are dissolved or dispersed in a solvent B. Auto paint is the most common type of paint examined in crime labs C. Layers of automobile paint 1. Electrocoat primer applied to the steel body of a car for corrosion resistance; colors range from black to grey 2. Primer surfacer applied to the primer to completely smooth it out and hide any seams or imperfections; highly pigmented (light grey for lighter colored cars and red oxide under dark colors) 3. Basecoat the actual color of a vehicle 4. Clearcoat unpigmented; improves gloss, durability, and appearance II. Microscopic Examination of Paint A. A microscope is the most important instrument for locating and comparing paint specimens B. Color is the most distinctive forensic characteristic of paint C. An examiner observes color layers and tries to match the number and sequence of colors. This process can connect paints to a common 1

2 origin D. Unfortunately, most paint specimens do not have layers that can be individualized to a single source, so a chemical analysis must be done III. Techniques Used in Paint Comparisons A. Characterization of paint binders 1. Pyrolysis gas chromatography a) Many solids cannot be injected into a gas chromatograph, so items must be heated, or pyrolyzed, to high temperatures so that they will decompose into gaseous products b) Then they are put into a chromatograph, and a pyrogram is produced showing the chemical makeup of the binder c) Even the smallest of paint chips can be pyrolyzed and sent through the gas chromatograph d) Pyrograms can distinguish one polymer from another 2. Infrared spectrophotometry a) Binders absorb infrared radiation to yield a spectrum that is characteristic to that specimen B. Characteristics of paint pigments 1. Emission spectrograph a) Can detect elements in auto paint simultaneously b) Some are common to all paints, but others have significant forensic uniqueness IV. Significance of Paint Evidence A. How to tell if two similar paints come from the same surface 1. Paint layers beneath the surface layer offer valuable points of comparison 2. Color charts for automobile finishes are available from manufacturers 3. Paint Data Query (PDQ) a) A database that provides information on paints based on make, model, and year b) Maintained by the Royal Canadian Mounted Police V. Collection and Preservation of Paint Evidence A. Paint evidence is mostly involved in burglaries and hit-and-run incidents B. Paint chips should be picked up with forceps and placed in a paper druggist fold or a glass or plastic container C. If the paint is smeared on or embedded into something, package the entire item D. With hit-and-run cases, collect uncontaminated paint from an undamaged area as a reference for comparison E. ¼-inch square samples are sufficient, but you must go all the way to the bare metal 2

3 Activities 1. Forensic Paint Crossword Puzzle. Have students review forensic paint analysis terminology by completing the Forensic Paint Crossword. It may be helpful to allow students to use their lecture notes. Use the Forensic Paint Crossword Puzzle Key for assessment. 2. Paint Layer Determination (this is a 2-day assignment). Prepare and distribute the materials before class. Divide the class into four groups (A, B, C, and D). Have the students create paint samples according to the procedure for Day 1 of the Paint Layer Determination Lab. For Day 2, have students analyze the samples and answer the lab questions (although they are working in groups, the students should complete the Day 2 work individually). See the Paint Layer Determination Lab Teacher s Notes and the Paint Layer Determination Lab for details. Use the Paint Layer Determination Lab Key and/or the Individual Work Rubric for assessment. Assessments Forensic Paint Analysis Quiz and Key Forensic Paint Crossword Puzzle Key Paint Layer Determination Key Discussion Rubric Individual Work Rubric Presentation Rubric Materials Forensic Paint Analysis computer-based presentation Forensic Paint Crossword Puzzle and Key Paint Layer Determination Lab Paint Layer Determination Lab handout (one per student) Paint Layer Determination Lab Teacher s Notes Paint Layer Determination Lab Key 4 index cards (3x5) 4 different colors of poster paint (to be shared among the 4 groups) 4 sponge paintbrushes (one for each color paint) 4 re-sealable sandwich bags (one for each group) Scissors (for each group) Forceps (for each group) Hand lenses or stereoscopic microscopes (for each group) Scrap paper or newspaper Colored pencils Resources Saferstein, Richard. Forensic Science: An Introduction. New Jersey: Pearson Prentice Hall,

4 Saferstein, Richard. Forensic Science: An Introduction. 2 nd ed. New Jersey: Pearson Prentice Hall, 2011 Saferstein, Richard. Criminalistics: An Introduction to Forensic Science. 8 th ed. Upper Saddle River, NJ; Pearson Prentice Hall, 2004B Accommodations for Learning Differences For reinforcement, students will write 3 test questions from the class notes and present them to the class. The questions must be one of each of the following: multiple choice, true/false, and completion. Use the Presentation Rubric for assessment (Note: The students questions may be used as additional items on the quiz or even as bonus questions). For enrichment, students will match paint chips to a crime scene sample. Obtain 3 to 4, ¼-inch sized paint chips from various items. Sources could include paint from houses, old bicycles, wrecked vehicles, etc. This activity will be more authentic if you use the same type of paint source (for example, three paint chips that come from 3 different red vehicles). Make sure you obtain 2 samples from each to allow for the crime scene sample. Label the crime scene sample and then label the other samples Sample A, Sample B, etc. Using the microscopes and the hand lenses, students are to try to determine which sample matches the crime scene sample. Use the Individual Work Rubric for assessment. State Education Standards Texas Essential Knowledge and Skills for Career and Technical Education Forensic Science (One Credit). (1) The student, for at least 40% of instructional time, conducts laboratory and field investigations using safe, environmentally appropriate, and ethical practices. These investigations must involve actively obtaining and analyzing data with physical equipment, but may also involve experimentation in a simulated environment as well as field observations that extend beyond the classroom. The student is expected to: (A) demonstrate safe practices during laboratory and field investigations; and (B) demonstrate an understanding of the use and conservation of resources and the proper disposal or recycling of materials. (2) The student uses scientific methods and equipment during laboratory and field investigations. The student is expected to: (F) collect and organize qualitative and quantitative data and make measurements with accuracy and precision using tools such as calculators, spreadsheet software, datacollecting probes, computers, standard laboratory glassware, microscopes, various prepared slides, 4

5 (G) (H) stereoscopes, metric rulers, electronic balances, gel electrophoresis apparatuses, micropipettors, hand lenses, Celsius thermometers, hot plates, lab notebooks or journals, timing devices, cameras, Petri dishes, lab incubators, meter sticks, and models, diagrams, or samples of biological specimens or structures; analyze, evaluate, make inferences, and predict trends from data; and communicate valid conclusions supported by the data through methods such as lab reports, labeled drawings, graphic organizers, journals, summaries, oral reports, and technology-based reports. (3) The student uses critical thinking, scientific reasoning, and problem solving to make informed decisions within and outside the classroom. The student is expected to: (A) (D) (E) (F) in all fields of science, analyze, evaluate, and critique scientific explanations by using empirical evidence, logical reasoning, and experimental and observational testing, including examining all sides of scientific evidence of those scientific explanations, so as to encourage critical thinking by the student; evaluate the impact of scientific research on society and the environment; evaluate models according to their limitations in representing biological objects or events; and research and describe the history of science and contributions of scientists. (5) The student recognizes the procedures of evidence collection while maintaining the integrity of a crime scene. The student is expected to: (C) (E) (F) (G) (H) (I) (J) conduct a systematic search of a simulated crime scene for physical evidence following crime scene protocol; describe the elements of a crime scene sketch such as measurements, compass directions, scale of proportion, legend, key, and title; develop a crime scene sketch using triangulation, rectangular coordinates, straight-line methods, and use of coordinates on transecting baseline; outline the chain of custody procedure for evidence discovered in a crime scene; demonstrate proper techniques for collecting and packaging physical evidence found at a crime scene; explain the functions of national databases available to forensic scientists; and collect and preserve physical evidence from a simulated crime scene. 5

6 (6) The student analyzes the evidence collected from a crime scene using scientific methods. The student is expected to: (A) demonstrate conversions of measurements between English and International System (SI) of units; (B) distinguish between physical and chemical properties of matter using the periodic table; (C) determine the elements within a compound or mixture; (D) identify the four types of chemical reactions; (G) identify the light sources used in forensic science such as ultraviolet light; (H) explain the examination of trace evidence using instruments such as a spectrophotometer, stereoscope, electron microscope, and compound microscope; (7) The student recognizes the methods to process and analyze trace evidence commonly found in a crime scene. The student is expected to: (A) perform continuous and light emissions laboratory procedures to identify trace evidence; College and Career Readiness Standards Science Standards I. Nature of Science: Scientific Ways of Learning and Thinking C. Collaborative and safe working practices 1. Collaborate on joint projects. 2. Understand and apply safe procedures in the laboratory and field, including chemical, electrical, and fire safety and safe handling of live or preserved organisms. 3. Demonstrate skill in the safe use of a wide variety of apparatuses, equipment, techniques, and procedures. 6

7 Name Date Matching Forensic Paint Analysis Quiz 1. The most important instrument for comparing paint chips 2. The layer of automobile paint that contains the actual color of the vehicle 3. A component of paint that is dissolved or dispersed in a solvent 4. The unpigmented paint layer that adds gloss and durability 5. Something an examiner would observe to match the number and sequence of colors 6. The most distinctive forensic characteristic of paint 7. The layer of automobile paint that hides imperfections 8. The process of heating a paint sample to high temperatures until it transforms into a gas 9. Radiation absorbed by paint binders to yield a spectrum that is unique to a specimen 10. One of the most common types of crime in which paint analysis is used 11. The database that provides information about automobile paint 12. The layer of automobile paint applied directly to the steel body for corrosion resistance 13. Capable of detecting elements in auto paint simultaneously 14. Should be collected from an undamaged area as a reference for comparison in a hit-and-run case 15. The minimum size of a paint sample for analysis A. Basecoat B. Binder C. Clearcoat D. Color E. Electrocoat Primer F. Emission Spectrograph G. Hit-and-Run H. Infrared I. Microscope J. Paint Data Query K. Paint Layers L. Primer Surfacer M. Pyrolysis N. Quarter-inch O. Uncontaminated Paint 7

8 Forensic Paint Analysis Quiz Key 1. I 2. A 3. B 4. C 5. K 6. D 7. L 8. M 9. H 10. G 11. J 12. E 13. F 14. O 15. N 8

9 Name Date Forensic Paint Crossword Puzzle Across: 1. Unpigmented paint layer; adds gloss and durability 5. Paint is composed of pigments and a 6. The most important instrument for comparing paint chips 7. When a paint sample is heated to high temperatures until it transforms into a gas 10. Most common type of crime where paint analysis is utilized Down: 2. Paint layer; hides imperfections 3. Absorbed by binders to yield a spectrum that is unique to a certain specimen 4. Examiner matches number and sequence of colors 8. Paint layer; actual color of a vehicle 9. The most distinctive forensic characteristic of paint 9

10 Forensic Paint Crossword Puzzle Key 6m i c r o s c o 2p e 4p a r 3i a s 8b i n 5b i n d e r m f n c 1c l e a r c o a t o 9c r a l a 7p y r o l y s i s r a t l u e y o r d e r f r 10h i t a n d r u n Across: 1. Unpigmented paint layer; adds gloss and durability (clearcoat) 5. Paint is composed of pigments and a (binder) 6. The most important instrument for comparing paint chips (microscope) 7. When a paint sample is heated to high temperatures until it transforms into a gas (pyrolysis) 10. Most common type of crime where paint analysis is utilized (hitandrun) a c e s Down: 2. Paint layer; hides imperfections (primersurfacer) 3. Absorbed by binders to yield a spectrum that is unique to a certain specimen (infrared) 4. Examiner matches number and sequence of colors (paintlayers) 8. Paint layer; actual color of a vehicle (basecoat) 9. The most distinctive forensic characteristic of paint (color) 10

11 Name Date Paint Layer Determination Lab Rationale: Oftentimes, paint consists of several layers of different substances, as is the case with automobile paint, or it may be several layers of different colors painted on top of one another. In the event that a paint chip is a piece of evidence, it may need to be compared to a known sample. Observation of paint layers is the first step in completing the comparison and does not destroy the sample as other methods of determination can. This activity provides an opportunity to observe and compare paint layers. Materials (needed per group): 3x5 cards, 1 per group Piece of scrap paper or newspaper 4 different colors of poster paint (or 1 color for each group, and they trade off) 4 sponge paintbrushes (1 per color) Resealable sandwich bag Scissors Hand lens or stereoscopic microscope Forceps Colored pencils Procedure (Day 1): 1. Place the 3x5 card on the piece of scrap paper or newspaper 2. Using the appropriate paintbrush, paint the entire surface of the card with one color of paint 3. Allow the paint to dry (it will dry faster if a hairdryer, fan, or incubator is available) 4. Once the paint is dry, choose another color and an appropriate paintbrush, and paint over the entire surface of the previous color 5. Repeat the steps until all 5 colors have been used (the sequence of colors used should be random among the groups) 6. When the card is completely dry, cut it into 8 equal pieces as illustrated 7. On the back, label 4 pieces with your group letter and leave the other 4 blank 8. Place all 8 pieces into the plastic bag and turn it in to the instructor 11

12 Procedure (Day 2): 1. Pick up a plastic bag and remove the contents using forceps. You will find 1 piece from each group (A D) and one labeled Crime Scene 2. Using either a hand lens or the stereoscopic microscopic, observe the different layers of paint 3. Compare each of the 4 group cards to the crime scene to see which one matches it 4. In the appropriate column, draw horizontal lines in colored pencil to represent the layers 5. Answer the questions that follow Top PAINT CHIP LAYERS Group A Group B Group C Group D Crime Scene Bottom Questions: 1. Did you determine which group matched the crime scene sample? If so, which one? If not, why? 2. Is it possible for the crime scene sample to match more than one group? How could that happen? 3. Would observation of paint layers alone be enough to determine an exact match? Explain your answer. 12

13 Paint Chip Determination Lab Teacher s Notes Review the Paint Chip Determination Lab materials. Use the following notes to prepare and lead the lab activity: If possible, make sure each group has a different sequence of paint layers. However, it is more challenging to have them all end up with the same color on top so they cannot automatically determine a match. If you choose, more paint color layers could also be used. After Day 1, remove all 8 samples from each bag. For the ones that have the group letter, divide them into 4 groups, each containing A D. For the remaining blank samples, choose one group to be the crime scene. On the back of those 4, write, Crime Scene. Discard all of the groups blank samples. When the samples are dispersed to the students for Day 2, each group should have 5 samples: A D and a Crime Scene. Place the cards back into the bags and distribute them to the groups to complete the lab procedure. 13

14 Paint Chip Determination Lab Key 1. Answers will vary depending on the class. Although it is tedious, students should be able to match the sample to the crime scene. 2. Yes, it is possible to have more than one group match the crime scene if the layers were painted in the same sequence. This could happen in reality, such as with cars that happened to be painted more than once with the same sequence of colors. 3. It would be difficult to allow color layers alone to be considered an exact match for reasons such as the explanation in #2 above. However, sometimes paint chips have a particular shape that may be matched to the source, much like a jigsaw puzzle. Most likely, if layers match a source, further testing would determine exactness. 14

15 Name Date Objectives 4 pts. Excellent Discussion Rubric 3 pts. Good 2 pts. Needs Some Improvement 1 pt. Needs Much Improvement N/A Pts. Participates in group discussion Encourages others to join the conversation Keeps the discussion progressing to achieve goals Shares thoughts actively while offering helpful recommendations to others Gives credit to others for their ideas Respects the opinions of others Involves others by asking questions or requesting input Expresses thoughts and ideas clearly and effectively Total Points (32 pts.) Comments: Copyright Texas Education Agency, All rights reserved. 15

16 Name Date Objectives Follows directions Student completed the work as directed, following the directions given, in order and to the level of quality indicated Time management Student used time wisely and remained on task 100% of the time Organization Student kept notes and materials in a neat, legible, and organized manner. Information was readily retrieved Evidence of learning Student documented information in his or her own words and can accurately answer questions related to the information retrieved *Research/Gathering information (if relevant) Student used a variety of methods and sources to gather information. Student took notes while gathering information Total Points (20 pts.) Comments: Individual Work Rubric 4 pts. Excellent 3 pts. Good 2 pts. Needs Some Improvement 1 pt. Needs Much Improvement N/A Pts. Copyright Texas Education Agency, All rights reserved. 16

17 Name: Date: Presentation Rubric Objectives Topic/Content Topic discussed completely and in-depth Includes properly cited sources (if used) Creativity/Neatness Integrates a variety of multimedia effects to create a professional presentation (transition and graphics) or appropriate visual aid used Title slide, table of contents, bibliography are included, using acceptable format Mechanics Grammar, spelling, punctuation, and capitalization are correct Image and font size are legible to the entire audience Oral Presentation Communicates with enthusiasm and eye contact Voice delivery and projection are dynamic and audible Audience Interaction Presentation holds audience s attention and relates a clear message Clearly and effectively communicates the content throughout the presentation 4 pts. Excellent 3 pts. Good 2 pts. Needs Some Improvement 1 pt. Needs Much Improvement N/A Pts. Total Points (20 pts.) Comments: Copyright Texas Education Agency, All rights reserved. 17