Anthro 245 1st Edition Lecture 3 Outline of Last Lecture I. The Scientific MethodOutline of Current Lecture II. CriminalisticsIII. EvidenceIV. Example and analysis of a case involving physical evidenceV. Significance of evidenceVI. Contamination and efforts to reduce contamination Current LectureThe Nature of Forensic Evidence Criminalistics - Scientific discipline that is cast with the recognition, collection, and individualization of physical evidence • People working in this field often have a Bachelors degree in areas like chemistry, biology, physics, etc. • They also specialize in areas such as crime scene investigation • Typically work in crime labs Evidence • Any object or statement by a witness that has bearing in a court of law • Types of evidence include: ◦ Testimonial evidence ◦ Subjective evidence - what a witness experienced ◦ Does not involve expert opinion ◦ Physical evidence ▪ Any physical object deemed to shed light on the case ▪ Objective ▪ Admissible in court via expert testimony Physical Evidence Continued: • Reconstruction evidence ◦ Information about events preceding, during, and after commission of a crime • Associative evidence ◦ Evidence used to associate or disassociate a suspect to a crime These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.• Gross - refers to a large amount of physical material (can be seen with the naked eye) ◦ Bullet, blood pool or smear, weapon • Trace - small bits of physical material (need a microscope) ◦ Latent impressions, blood, hairs, fiber, soil Common Types of Evidence Found: • Bodily fluids • Drugs • Documents • Fibers • Tool marks • Explosives • Serial numbers • Maggots Locard's Exchange Principle Revisited • Edmund Locard (1877-1966) • Every contact leaves a trace • Cross-transfer of evidence between participants and the scene • The nature and duration of the contact dictates the amount of transfer Utility of Physical Evidence: • Define the crime (corpus delict) ◦ Did the crime happen? ▪ Type of weapon used ▪ Whether suicide or homicide, or homicide or accident • Provides investigation leads • Define the Modus Operandi ◦ How the crime occurred ▪ A burglar who uses the same tools ▪ A rapist who always uses the same weapon • Identification of suspect and victims • Link suspect to victim/crime scene • Corroborate or refute a suspects story • Exonerate innocent ◦ Exculpatory evidence - exclude people who should be excluded • Induce a confession • Reconstruction of a crime • Provide testimony in court ◦ Expert witness to talk and make inferences about the evidence Example of physical evidence: • Series of similar sexual assaults between 1988 and 1991 in Michigan and Ohio ◦ Man abducted male and female victims while they were travelling down rural roads either on a bike or on foot◦ Drove by a few times before stopping to ask them for help ◦ Forced them into the passengers seat at gunpoint and forced them to remove clothes, covered their eyes, bound their hands with duct tape or rope ◦ Took them to a remote location where he whipped them and forced them to preform oral sex ◦ Made them recollect their own clothes and then took the bindings back • Man drove a white car with blue interior • Cat hairs and blue fibers found on clothes of 15 year old male victim • Blue Fibers analyzed and found to be polypropylene, common in cars • 2 months later a 19 year old female is attacked in a similar way • Witnesses later reported seeing a white car in the area around the time of the attack ◦ He allowed her to keep her socks on ◦ Found four fibers on her socks ▪ One similar to the fiber from the male victim's clothes ▪ Three fibers were different so GM was contacted - fibers used in select older GM cars, but this information did not narrow the list enough • Police now knew about the car • Had a better ID of the vehicle ◦ Identification from herringbone pattern on emergency brake because the victim could see below the duct tape Comparison of Fibers: • Examine ◦ The number of fibers in each strand ◦ The diameter of strands and fibers ◦ Direction and the number of twists ◦ Type of weave ◦ Dye content ◦ Any embedded material • Determine ◦ The type of fiber ◦ Natural or man-made ◦ Color and shade ◦ Expected use or application ◦ Manufacturer and period of manufacture ◦ Relative rarity of the fiver Evidence was used during the trial - it was all circumstantial evidence, but it was A LOT of circumstantial evidence and it resulted in a conviction Significance of physical evidence • This case had no DNA or fingerprint evidence • In this case physical evidence: ◦ Gave investigation leads ◦ Corroborated victims' stories and helped define the modus operandi ◦ Linked a suspect to the victims◦ Excluded the innocent (other people driving the same type of car without the relatively rare herringbone pattern on the emergency brake) ◦ Provided experts with testimony to give in court Circumstantial evidence is evidence that requires inference Contamination • Locard's principle also applies to contaminating evidence • Defense teams use contamination or possible contamination to introduce reasonable doubt ◦ Remember that the prosecution must prove a defendant is guilty beyond a reasonable doubt Main sources of contamination: • Scene investigators who contaminate evidence ◦ Sneezing into samples ◦ Shedding hair and skin over scene ◦ Walking through blood and other substances and leaving a trail of their own footprints • Laboratory personnel who analyze evidence ◦ Mislabeling ◦ Machines not cleaned properly Efforts to reduce contamination: • Crime scene ◦ Wear personal protective equipment ▪ Gloves for your hands and booties to put over shoes ◦ Using separate bags for each piece of evidence and using clear labels • Laboratory ◦ Difference spaces and different examiners to analyze victim and suspect evidence ◦ Quality assurance and proficiency testing • Maintain chain of custody Chain of custody: • Documentation, maintenance, and preservation of evidence from the moment it is collected until it is presented in court • Typically a physical piece of paper with a bar code • Everyone who comes in contact with the evidence must