Chapter 3

1. Chapter 3 Forensic Laboratory Techniques

2. Where is Laci? 1. How might investigators analyze the white powder on Peterson’s boat? 2. Is the fact that the hair found at the warehouse is consistent with Laci’s hair class evidence or individual evidence? Explain. 3. How might investigators identify the remains as Laci and Conner?

3. Introduction Questioned samples vs controls Physical properties – can be measured without changing the identity of the evidence Ex) density = mass/volume color, melting point, boiling point, odor, and viscosity cutting, shredding, melting or freezing = physical changes

4. Introduction Chemical properties- determine how a substance behaves in the presence of other substances Ex) iron + oxygen + water = rust Rusting, burning, decomposing = chemical changes(alters its chemical identity)

5. Presumptive and Confirmatory Tests Presumptive tests – screen evidence to reduce the number of possibilities Ex) red stain  blood? -Yes Remaining question? Confirmatory tests – used to make more specific identification Ex) Blood human or animal?

6. Presumptive and Confirmatory Tests Lab tests on body fluid chemical test microscopy DNA profiling Presumptive testing – reduces cost and saves time by not collecting evidence that is not essential to case

7. Microscopy 1. Compound Light Microscope – light and multiple lenses - magnifies between 40 and 1000 x(see fig. 3-4) - used to examine hair, fibers 2. Stereomicroscope – light is reflected from the surface - produces a 3-D image - used to examine insect larvae, paint chips

8. Microscopy 3. Comparison Microscope – side-by-side comparison Ex) bullet striations, fibers, and hair samples 4. Electron microscopes – use beams of electrons to form images - can magnify up to 500,000 times - 2 types – transmission and scanning(interior vs surface) - Ex) gunshot residue

9. Chromatography Quantitative vs qualitative analysis – measurable amount vs a description or identification of the components of a mixture Qualitative tests based on physical and chemical properties - ex) chromatography – separates substances within a mixture based upon their physical properties such as solubility

10. Paper Chromatography http://www.gcsescience.com/e8-chromatography.htm

11. Other types of chromatography Thin-layer – stationary phase is a thin layer of gel-like material on a glass or plastic plate(faster and clearer) - used for separating dyes and inks Gas – performed at high temperatures - used for separating mixtures containing large molecules such as the proteins found in blood High-performance liquid – can take place at room temperature - used to test for the presence of flammable materials such as explosives or accelerants

12. Electromagnetic Radiation http://www.sengpielaudio.com/SpectrumOfElectromagneticRadiation.gif Light travels in electromagnetic waves Wavelength – the distance between two consecutive crests Frequency – how many waves pass a specific point within a given time Electromagnetic spectrum – used to search for latent fingerprints, examine articles of clothing for trace evidence, or determine the structure of a molecule

13. Spectroscopy How Does Spectroscopy Work? Imagine that light is food and the sample is a room full of people, a complete spectrum of light would be like giving all the food in a grocery store to the people in the room. As you might imagine, almost all of the food would be wasted (transmitted). But some of the food would be eaten (absorbed). Now imagine that you knew there was only one person who would always eat broccoli. If all of the broccoli came through the room uneaten, that person must not be in the room, but if some were missing, you would know that person was in the room. Furthermore, no matter how much asparagus you put in the room, the broccoli-lover would never eat any, and so adding asparagus would never tell you if the broccoli-lover was in the room or not.

14. Forms of spectroscopy 1. Mass spectroscopy – takes into account the mass to charge ratio 2. Atomic absorption spectroscopy – measures the amount of a specific wavelength absorbed by atoms of a particular substance(useful in determining heavy metal contamination of soil, air, and water) 3. Ultraviolet spectroscopy – measures wavelengths of light and used to determine the concentration of different elements in a solution(used to detect drugs in blood or urine, analyze components of dyes and food additives, and monitor air and water quality

15. Fingerprint-developing techniques Latent = invisible A) UV light B) Dusting – best for “fresh” fingerprints C) Cyanoacrylate fuming – heat + cyanoacrylate reacts with fatty acids and proteins fingerprints become whitish D) Silver nitrate – perspiration + silver nitrate + UV light  fingerprints appear black E) Ninhydrin – for porous surfaces – ninhydrin + amino acids  purple fingerprint

16. Fingerprint-developing techniques F) Diazofluoren – same mechanism as ninhydrin, but faster G) Vacuum Metal Deposition – best on non-metal surfaces, gold attracted to tissue and zinc is attracted to the gold

17. Fingerprint Databases Latent fingerprints developed photographed scanned digitized FBI – maintains the Integrated Automated Fingerprint Identification System(IAFIS) http://www.fbi.gov/news/stories/2013/july/2013-latent-hit-of-the-year-award

18. DNA Analysis Deoxyribonucleic Acid – found in the cells of all organisms Individual evidence http://www.umass.edu/molvis/tutorials/dna/ DNA fingerprinting http://dnafingerprinting19.tripod.com/sitebuildercontent/sitebuilderpictures/dna-evidence3.jpeg http://www.pbs.org/wgbh/nova/education/body/create-dna-fingerprint.html