Science of Crime Scenes Chapter 2.1 - PowerPoint Presentation

1. Science of Crime ScenesChapter 2.1Science of Crime Scenes1

2. Intelligence: the ability to solve problemsTactical supports the investigation of a particular case or suspect; a bank in a particular location that was robbed on a specific day, for example.Operationalsupports the management of resources to solve a group of related problems; a string of bank robberies that all share similar patterns of execution, for example.Strategicsupports broad approaches to improving policies and strategies; an agency may, for example, allocate funds to train personnel to better process documents—like bank robbery notes—for fingerprints.Science of Crime Scenes2

3. A variety of sources of intelligencePeople (human intelligence or HUMINT)Electronic transmissions (signals intelligence or SIGINT)Geographic and geologic (GEOINT)Public or open sources (open-source intelligence or OSINT)Measurements and signatures (MASINT)Science of Crime Scenes3

4. The intelligence cyclePlanning and direction: determining the needs of the consumer and prioritization of resources.Collection: gathering raw data from various sources.Processing: converting the collected information into a usable format.Analysis and production: analyzing the processed information and turning it into finished intelligence; resolving data conflicts; and producing reports, evaluations, reliability statements, and other analytic services—hence the use of the term production.Dissemination: distributing intelligence reports to consumers.Science of Crime Scenes4

5. Crime scenes are like intelligenceScience of Crime Scenes5

6. Connections through Contact: Transfer and PersistenceLocard’s Exchange Principlewhen two things come into contact, they exchange information, even if the traces are not identifiable or are too small to be found The results of such a transfer is proxy data, or evidenceThe transfer is the mechanism of revealing the relationships between those involved in a criminal activity The evidence itself relates more to the specificity and resolution of the statements that can be made Essentially all evidence is transfer evidence and the form of evidence relates to what can be said about the transfer. Science of Crime Scenes6

7. Science of Crime Scenes7ItemTransferred From (Source)Transferred To (Target/Location)DrugsDealerBuyer’s pocket or carBlood stainsVictim’s bodyBedroom wallAlcoholGlassDrunk driver’s blood streamSemenAssailantVictimInkWriter’s penStolen checkHandwritingWriter’s hand/brainFalsified documentFibersKidnapper’s carVictim’s jacketPaint chips/smearVehicleHit-and-run victimBulletShooter’s gunVictim’s bodyStriationsBarrel of shooter’s gunDischarged bulletImperfectionsBarrel-cutting toolShooter’s gun’s barrel

8. Conditions affect evidence transferThe pressure applied during contactThe number of contacts (many contacts between two objects should result in more transferred material than one contact)How easily the item transfers material (liquid blood transfers more readily than does dried blood, for example)The form of the evidence (solid/particulate, liquid, or gas/aerosol)How much of the item is involved in the contact (a square centimeter should transfer less than a square meter of the same material)Science of Crime Scenes8

9. The Five-Second RuleIf a piece of food is dropped on the floor, how long can it sit there and still be edible? The popular joke is five seconds, leading to “The Five-Second Rule”Researchers found that bacteria (Salmonella) survived on wood, tiles, and carpet after 28 days Bread and bologna were contaminated in under five seconds; after a minute, the contamination increased significantly Longer contact results in more transfer Science of Crime Scenes9

10. Persistence Once the evidence transfers, it will remain in that location until it further transfers, degrades until it is unusable or unrecognizable, or is collected as evidence How long evidence persists depends on:What the evidence is (such as fibers, blood, toolmarks, chemicals)The location of the evidence (on the surface, in a pocket, under water)The environment around the evidence (dry, cold, wet, hot, moving)Time from transfer to collection (seconds, minutes, days, years, decades)“Activity” of or around the evidence location (a tire on a moving car versus a deceased individual)Science of Crime Scenes10

11. Some evidence is more temporary Fragile or temporary evidence, like trace materials such as hairs or fibers, should be collected first Other types of evidence, like dried blood stains, will persist far longer and can be collected laterThis planned collection order, however, may change under emergency circumstances Like sudden weatherScience of Crime Scenes11

12. Classification and ResolutionAll things are considered to be unique in space and time and no two objects are absolutely identical Science of Crime Scenes12

13. Example: Polo shirtA manufacturer may produce thousands of shirts of a particular type each year Consumers demand consistency of products and their performanceThe manufacturer’s goal is to produce shirts that all look and perform the same In forensic work, this consistency serves two purposes:First, the consistency between similarly manufactured objects makes it easy to separate one item from another (this red polo shirt is different from this white one).Second, the consistency within objects made by the same manufacturer makes it difficult to distinguish items with many of the same characteristics (two red polo shirts).Science of Crime Scenes13

14. Example: Polo shirtThink about two white polo shirts that come off of the same production line one after the otherOther than labeling them “#1” and “#2,” it could be very difficult to separate them once they were placed together But what if the two shirts are exactly the same except for color: One is white and one is red. Although they can be easily distinguished (the red one; the white one), are they in the same category? The two polo shirts have more in common with each other than with a blue dress shirt. All shirts, however, are more alike than any of them are compared to, say, a shoe Science of Crime Scenes14

15. Biology is similarAn organism is the combination of its genotype (the genetic material that is encoded in its DNA) phenotype (the expression of its genetic potential in a given environment)In some ways, biological specimens are far more specific than manufactured onesIdentifying a suspect or a missing person by their DNA profileIn other ways, however, some forms of biological information are more like manufactured items The wood from one oak tree will look more similar to another oak tree than it would to a mapleScience of Crime Scenes15

16. The point: IdentificationThe result of the examination of the chemical and physical properties of an objectThe results of the examination categorize the object as a member of a groupWhat the object is made of—its color, mass, and/or volume—and many other traits go into identifying it as being a particular thingAll of the characteristics used to identify an object help to refine that object’s identity and its membership in various groupsScience of Crime Scenes16

17. Example: Dog hairsCrime scene debris has fibrous objectsClassification/IdentificationHairsNon-human hairsDog hairsBlack Labrador Retriever hairsClass is a scalable definitionJust knowing they are dog hairs may be enough for the purposes of the investigationScience of Crime Scenes17

18. A “common source”For example, take an automotive paint chip: What’s the “common source”?The manufacturer (to distinguish it from other similar paints)The factory (to determine where it was made)The batch or lot of production (to distinguish it from other batches at the same factory)All the vehicles painted with that color paintThe vehicle painted with that color paint involved in the crime in questionScience of Crime Scenes18

19. Even “common” items may varyEven something perceived to be very common, like sand, can have a wide variation. Top to bottom: Rodeo Beach, Marin County, CAAgate Beach, ORDaytona Beach, FLBermudaSantorini, GreeceAyers Rock (Uluru), AustraliaSahara Desert, MauritaniaOld Course Beach, St. Andrews, Scotland.Science of Crime Scenes19

20. Individualization of EvidenceIf an object can be classified into a group with only one member (itself), it is said to have been individualizedAn individualized object has been associated with one, and only one, source—it is uniqueIndividualization is the logical extension of classificationScience of Crime Scenes20

21. Individualization rests on two assumptionsAll things are unique in space and timeThis is inherently unprovableYou can’t compare one piece of evidence to everything else in the universeThe properties by which a thing is classified are constant over timeEntropy: Nothing stays the same foreverForensic science is relegated to making interpretive statements based on statistical methods because it deals with so many uncertaintiesScience of Crime Scenes21

22. Individualization is bankruptThe gap between the controlled laboratory and the real world is central to forensic science’s fundamentalsUncertainty is everywhereEven in DNA analysis, where each person’s genetic material is known to be unique, statistics are used. Statistics are, in fact, what give forensic DNA analysis its power Individualization, with very few exceptions, is an intellectually bankrupt concept in forensic science.Science of Crime Scenes22

23. Relationships and ContextThe relationships between the people, places, and things involved in crimes are critical to deciding what to examine and how to interpret the resultsThese relationships also feed the intelligence work of the current investigation and related onesScience of Crime Scenes23

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25. Relationships and ContextIt is important to establish the context of the crime and those involved early in the investigation This sets the stage for what evidence is significant, what methods may be most effective for collection or analysis, and what may be safely ignored Evidence collection based on intelligent decision making produces a better result in the laboratory and the courtsFear of missing something is not a strategyScience of Crime Scenes25

26. Known and Questioned ItemsQuestioned items come from an unknown original sourceKnown items come from a known original sourceHit and run case exampleScience of Crime Scenes26EvidenceCarVictimPaintKnown (taken from car)Questioned (taken from victim)Fibers Questioned (taken from bumper)Known (taken from victim’s shirt)