Presentation on theme: "Monday March , 2013 AIM: How does the forensic"— Presentation transcript:
1 Monday March , 2013 AIM: How does the forensic examination of paint give insight tosolving a crime scene?DO NOW: How does microscopic analysis help investigate forensic evidence?Homework: Text Read pages Forensic analysis of paint. Answer the following1- What is the function of a binder?2- What happens to the paint after applied to the surface?3- What is one of the most common types of paint examined in a crime lab?4- List and describe the 4 organic coatings applied to automotive steel.
2 Motivation How would you analyze the paint chip displayed? List at least 4 observable characteristics.
3 PAINT: Coating consisting of 3 classes of paint Pigments a polymeric film former (binder)a suspending medium or solvent3 classes of paintOil basedWater basedSolvent based ( varnish)
4 Tuesday 3/5/13 AIM: How does a paint mixture break down? DO NOW: How does the forensicexamination of paint give insight tosolving a crime scene?HOMEWORK: Textbook read pages Explain how microscope analysis helped solve the Lindbergh kidnapping
5 Paint is an example of trace evidence Transferred by:Car accidentsCar-carCar-victimWet paint leaving a mark or imprintMicroscopic transfer on to a tool used to commit a crimeEx: crobar used to break open a door
6 Paint is an example of trace evidence Analyzed by:Layers of a chipIngredientsCustom coloringchromatography
7 Paint is a mixture Pigment (color) Modifiers (change pigment) Blues and greens are organicReds, yellows, whites: inorganicModifiers (change pigment)Control the property of the paintGloss, flexibility, durability, toughnessExtenders (keep pigment)Add bulk and covering capacityInorganicBinders (help paint stick to the surface)Natural or syntheticStabilizes the mixtureForms a film when spread
8 Automobile Coatings or Layers of paint Electrocoat Primer – the first layer applied to the steel for corrosion resistance.Primer surfacer – smooths out and hides imperfectionsBasecoat or Undercoat – provides color and represents the “eye appeal” of the finishClearcoat or topcoat – resists UV radiation and acid rain
12 Each layer is uniqueTop coat, primer and undercoat all have different chemical compositionsExposure to chemicals, dirt and rain can complicate analysis
13 A man was killed by riding his bike late one night A man was killed by riding his bike late one night. The defendant was charged with failure to stop at the scene of a serious personal injury accident. As a forensic scientist how do you think the defendant was caught.
14 Are these paintings the same or is one forged. How can you tell Are these paintings the same or is one forged? How can you tell? Explain in detail.
15 In your groups hand in only 1 sheet 1- Place your heading listing ALL group membersQuestions:1- What is the crime?2- List some of the initial evidence found by the police3- What did the witnesses say?4- What kind of car did John Vollman drive?5- How was Vollman found guilty?6- What information was gathered by the autopsy?7- Define NAA8- How did the NAA help solve this case?9- What year did Vollman get convicted
16 Wednesday 3/6/13 AIM: How does a paint mixture break down? DO NOW:Which layer of car paint is the most informative and WHY?Homework: Textbook Read page Answer questions on page Write out the question followed by the answer
17 DO NOW answerUndercoat more than any other property, gives paint its most distinctive forensic characteristics.contains most pigment
18 MotivationThrift Store Masterpiece? Teri Horton, a retired truck driver, talks with CNN's Anderson Cooper about a painting she bought years ago that she believes is the work of famed painter Jackson Pollock. Hortonbelieves her painting is worth about $50 million Some experts disagree.Is it or isn't it? How would you tell?
20 How would you determine if a painting is real or fake?
21 How would you collect paint samples from a crime scene?
22 Video showing Tower Bridge paint analysis | Tower Bridge
23 How would you collect samples of paint at a crime scene?
24 London tower bridge built in 1894 Extract paint chip samples by first placing a piece of masking tape over an area, smacking it with a chizzle then remove the tapeHelps to establish each layer as undercoat, primer, finishing coat etc.Layers of dirt defines the upper layer of finish coatAlso tells you about the environment the paint was exposed to1956 clean air act: no dirt layer
25 London bridge tower continued Dirt helps to determine the time frame of the layerComparing layers allows to determine how the bridge looked and was changed through out history
26 Collecting paint from a crime scene Found on a variety of objectsClothingVehiclesToolsFurnitureMixed with dirt or greaseUndermost layer is the most informativeMatching chips with flakes individualize evidence therefore preservation is extremely importantUse of dental drills and scalpals are the most often used tools
27 Thursday 3/7/13 AIM: How can we analyze each layer of a paint sample? DO NOW:List at least 5 characteristics you would use if this paint chip was found at a crime scene.AIM: How can we analyze each layer of a paint sample?Homework: Textbook read page 201 Case analysis answer the questions on the next slide
28 Paint analysisNarrow down a paint sample to the year, make and model of productionFind the factory that produced the paint and the dealership it was first sold
29 Thursday 3/7/13Homework: Textbook read page 201 Case reading the central park rapistQuestion 1- Who were the original suspects in this case and why were they suspected of the rape?Question 2- What did the forensic analyst in this case testify to?Question 3- Even though semen samples did not match, why were the suspects convicted?Question 4- Who was the central park rapist and how was he caught?
30 Paint: inorganic and organic Causes different chemical analysis of different types and colors of paint chips.Microscope: traditional and most important in locating and comparing paint specimensAnalysis at times magnification reveals paint layersIdentifies each individual layer
32 AssessmentHow would you collect a paint sample from a car which is suspected of a hit and run?
33 Paint chip and flake analysis The number of layers is determined by variety of microscopic techniqueCompare flakes to known or control samples easiest technique is to match fractured edges to an area of paint lossInvestigators use light microscopes, stereomicroscopes and sometimes scanning electron microscopes to look for jigsaw fits
37 Analysis of paint Stereoscopic microscopes Compare known specimens ColorSurface textureColor laying sequenceLayers of different colored paint are very helpful in matching an unknown to a known sample
38 Analysis of paint Micro-spectrophotometry Helps determine nature of pigments by reflecting light through themInfrared spectrometry: determines organic componentsX-ray powder diffraction determines microcrystalline components
39 Top four: cross sections of different samples and underlying layers of red paint of different red automobilesBottom Four: cross sections of common red household paint
40 Pyrolysis Pyro: Fire Lysis: to break Gas chromotography Chromotography: separates paint according to colorPaint is vaporized and injected into a gas chromotograph which separates paint into its components
42 Mass spectrometrySeparates paint chip components based on molecular weightEach pigment has a different molecular weightCreates a chemical fingerprint that can be compared to reference samples
43 Royale Canadian Mounted Police Created a database called Paint Data QueryContains chemical composition of paint from most vehicles sold in North America after 1973International databaseUsed by forensic scientists to test unknown samples found at crime scenesFBI: has a similar database of more than 40,000 paint samples
44 Thursday 3/7/13Homework: Textbook read page 201 Case reading the central park rapistQuestion 1- Who were the original suspects in this case and why were they suspected of the rape?Question 2- What did the forensic analyst in this case testify to?Question 3- Even though semen samples did not match, why were the suspects convicted?Question 4- Who was the central park rapist and how was he caught?
45 Last night homework answers 1- 5 teens were arrested because they were walking out of the park around the time of the rape 2- hair fibers on the teens clothes match those found on the victim 3- Hair fibers match 4- Matair Reyes was found to be the central park rapist because his semen sample matched!
46 Text read pages 260-261 in your notebook write out and answer Who are the suspects?What are the crimes?What are the pieces of evidence at each crime scene?When and what was the major break in the case?What roll did paint play in the capture of the suspects?How were all the crimes connected?
47 Textbook read pagesJames Tyler Williams and Benjamin Mathew WilliamsJune 18,1999- Burned synagoguesJuly 1, Killed a gay couple Gary Matson and Winfred MauderMarch Medical abortion building arson
48 AssessmentHow is micro-spectrophotometry similar to gas chromatography?They both separate a paint sample into each color it is composed of.
49 AIM: How can we separate paint chips based on their molecular structure? DO NOW: Explain the difference in how the stereoscopic microscope and the Micro-spectrophotometry separate paint chips.Homework: Study for quest tomorrow
50 Create a list: Why do we even want to analyze paint chips? MotivationCreate a list: Why do we even want to analyze paint chips?
51 Monday 5/7/12AIM: How can paint chips be chemically broken down into different colors?DO NOW: List some characteristics of paint that help to individualize itHomework: Study for TEST on WEDNESDAY
52 Friday 5/4/12AIM: How can forensic scientists physically separate paint chip samples?DO NOW: textbook page Read the lab and answer questions 4 and 5 in your notesEXAM TUESDAY CHAPTER 8. check the website for review topics