Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Presentation developed by T. Trimpe 2007 http://sciencespot.net • What is the difference between: • Class Evidence & • Individual Evidence? • One of the primary endeavors of forensic scientists must be to create and update statistical databases for evaluating the significance of class physical evidence. • The chances of finding class physical evidence are much greater than individual physical evidence. Assessing the Value of Evidence: • The value of class physical evidence lies in its ability to corroborate events with data in a manner that is, as nearly as possible, free of human error and bias. • It is the thread that binds together other findings. • The chances of finding two identical pieces of physical evidence at a crime scene that did not originate from the same source are low. • As the number of objects linking an individual to a crime scene increases, the likelihood that he/she was involved increases dramatically. Cautions and limitations in dealing with physical evidence: • The weight of significance of physical evidence is left entirely to a jury of laypeople. • Physical evidence may also be used to exclude a person from suspicion. • The task of the forensic scientist is to find as many characteristics as possible to tie one substance with another. • For forensic examiners, reading text books and relevant journals is no substitute for experience. • In a criminal investigation, the ultimate contribution that a criminalist can make is the linking of a suspect to a crime through comparative analysis. Fingerprint databases: • Integrated Automated Fingerprint Identification Systems (IAFIS) – a national fingerprint and criminal history database maintained by the FBI and launched in 1999. • Once the quality of the print is deemed suitable for the IAFIS search, the examiner creates a digital image of the print. • Then the examiner marks points on the print to guide the search. • The print is then electronically submitted to IAFIS. • Within minutes, the examiner may receive a list of potential matches and their corresponding fingerprints for verification. DNA Databases: • In 1998, the FBI’s Combined DNA Index System (CODIS) became fully operational. • CODIS Creates investigative leads from 2 sources: • The forensic index. • The offender index. • The forensic index currently contains 110,000 profiles from unsolved crime scene evidence. Based on a match, police in several jurisdictions can identify serial crimes. • The offender index contains profiles from nearly three million convicted or arrested individuals. • Hundreds of thousands more are backlogged and waiting for entry into the system. Other Databases: • National integrated Ballistics Information Network (NIBIN) maintained by the Bureau of Alcohol, Tobacco and Firearms. • Firearms and explosives – allows analysts to acquire, digitize, and compare markings made by a firearm on bullets and casings. • The heart of this database is the (IBIS) Integrated Ballistic Identification System. Comprising a microscope and a computer unit that can capture an image of a bullet or cartridge casing. Images are forwarded to a regional server. • IBIS does not definitively match a bullet to a firearm. It merely provides a list of candidates that the investigator can follow up on. • Database contains chemical and color information pertaining to original automotive paints. • Developed and maintained by the Royal Canadian Mounted Police. Contains information on the make, model, year and assembly plant of more than 13,000 vehicles (types). Also has a library of more than 50,000 layers of paint. • Greatest use in hit-and-run cases. SICAR (Shoeprint Image Capture and Retrieval) – • a NONgoverment database. • Commercially available, used for comparing and identifying crime scene shoeprints. • Can link a crime scene shoe impression to a particular shoe manufacturer. • Tread Assist – Tire Impressions. What is impression evidence? • Impression evidence can be defined as objects or materials that have retained the characteristics of other objects through direct contact. • Impressions are created when one object is pressed against another material with enough force to leave an impression of the object. • Shoeprints, tool marks, tire tracks, bite marks, and marks on a fired bullet are several examples of impression evidence. • Impressions may be found in or on many different types of materials. • The quality of the impression depends on: • the object making the impression. • the surface conditions, such as how hard or soft it is and what type of material it is (soil, mud, dust, concrete, grass, skin, etc.) 2-D: • This type of impression is documented using photography. • Some impressions may be dusted with fingerprint powder to be photographed or lifted with tape. • They may also be collected using an electrostatic dust lifting process. 3-D: • This type of impression can be documented using photography as well as by casting, which involves using dental stone or a similar substance to preserve the dimensional characteristics of the print. Collection Methods Investigators analyze the impression evidence to find unique characteristics to link shoes, tires, tools, and other objects found in a suspect’s possession to evidence at a crime scene. Collection of impression evidence can be accomplished using several methods: Example of Shoe Print in Bio-Foam Impression Foam Tire Track Evidence • Tire tracks are important in forensic investigations and are usually found in road accident scenes or in the access and escape routes of other crime scenes. • Tracks help investigators identify the type of vehicle that left them. • Investigators may make ink prints of a tire or plaster casts of a track. They will also take photographs that can later be used to prove a match. Features to analyze: • Tread pattern. • Width & depth of the tread pattern. • Unique characteristics due to the wear pattern or defects. • Tire databases are available help investigators determine the brand and model of the tire that left the impression , which can be used to determine the type of vehicle that made the tracks. Tool Mark Evidence • Certain defects or patterns may be left on a tool when it is made or used, which can be used to find matches between evidence at a crime scene and tools or objects found at a suspect’s home. “Stocking Strangler” – bite mark impressions. Tool marks can be classified two ways: • Impressions – As a tool hits a softer surface, the shape of the tool and imperfections in its surface may be left behind as an impression. • Scratches – As a tool moves across a surface, it may leave ridges or striations behind. NOTE: Some tool marks are a combination of both types. Features to analyze: • Dimensions of the impression. • Ridges or striation patterns. • Defects, such as nicks and chips. • Paint chips or metal shards left on a tool. Shoe Print Evidence • Investigators can analyze a shoe print to determine its class, or the type and brand of shoe. They will also look for individual characteristics, such as wear patterns and specific damages or defects. • Databases of shoe prints are help investigators determine the brand of shoe to provide leads for a case. STAMP Database Bite Mark Evidence • Investigators can analyze bite marks for characteristics to help them identify victims or suspects as well as to exclude others. • Marks can be left on a victim’s skin or other objects, such as Styrofoam cups, gum, or foods. • Dental records including xrays can also provide useful information, especially when attempting to identify a victim. Bite Mark Evidence Video Features to analyze: • Type of bite mark (human or animal). • Characteristics of the teeth (position, evidence of dental work, wear patterns, etc.). • Color of area to estimate how long ago the bite occurred (old or recent bite). • Swab for body fluids for DNA tests. Did you know? The most famous incident where bite mark evidence led to a conviction, was in the case of the notorious serial killer, Ted Bundy. He was responsible for an undetermined number of murders between 1973 and 1978 and was finally tied to the murder of Lisa Levy through bites that he had inflicted on her body. • • • • Dental training Licensed dentist Special classes and seminars Forensic Odontology certification from American Academy of Forensic Science • Comparison of antemortem data with postmortem data. • Presumptive vs. positive identification. • Presumptive = to the best of our ability to determine, this is the person. • Positive = we know this is the person. • • • • Dental record comparison DNA Fingerprints Radiological • Primary (deciduous set) – 20 teeth • Secondary (permanent set) – 32 teeth • Maxillary set • RU quadrant • LU quadrant • Mandibular set • RL quadrant • LL quadrant • Incisors • Central and lateral • Canines • Premolars (bicuspids) • First and second • Molars • First, second and third • Using a pre mortem x-ray and a dental chart any major construction is marked on the dental chart. • Using a post mortem x-ray and a dental chart features are also marked. • Comparative overlays of teeth angles and separations are also used to positively identify decedents. • Often there are bite marks that can be used to identify perpetrators (Ted Bundy). • Photographic study and image enhancement with comparative study may exclude or positively identify a suspect. • Most often seen in rape, murder, child abuse and spousal abuse.