The Impression that I get!

Two types of impressions Indentations: made in soft material - wet dirt, clay, snow Residue: from surface of object - blood or dirt Chemicals can be added to footprint evidence to develop footprints made in blood

Preservation of Impression •Original is best •Photograph all impressions in case of damage •Handprint (sticky material) or Pathfinder (electrostatic) used to lift residue impressions •Casting used for indentations

Tread Nomenclature and Sidewall Information

Tread Nomenclature and Sidewall Information Department of Transportation number, known as DOT number – consists of:

Tread Nomenclature and Sidewall Information Retread tires – have slightly different numbers DOTR YPY 1201 DOTR – Department of Transportation retread YPY – Manufacturer retread 1201 – date and year of manufacture

Tire Track Evidence Tire track evidence consists of: Tire track width Wheelbase dimensions Turning diameter Relative positions of turning tracks

VIII. Tire Track Evidence 1. Tire track evidence consists of: Tire track width Wheelbase dimensions Turning diameter Relative positions of turning tracks

1. Track Width (Stance) The measurement made from the center of one wheel or impression to the opposite wheel or impression Front stance is normally different from the rear width When a vehicle is traveling forward, the rear tires will track over the tracks left by the front tires

If a vehicle is turning, the track width between the front wheel will become narrower and cease to be a reliable measurement The rear tire stance will stay the same Databases can produce lists of vehicles that have the same stance dimensions

2. Wheelbase measurement of center of hubs of front wheels to center of hubs of rear wheel normally not present at crime scenes, unless the tracks show evidence of being parked

3. Turning Diameter Diameter of circle a vehicle makes when its steering wheel is fully turned pertains to front wheels only Smaller cars have a smaller turning diameter Formula for calculating turning diameter: Turing Diameter = (B²/A) + A, B = distance between two points ( x and x’) on turn circle A = distance between outer margin and a mid point between x and x’

4. Tire Positions in a Turn When a vehicle moves in straight path, the rear tires run directly over the front tires So there are only two sets of tracks to recover only rear tire tracks When a vehicle turns, rear and front tires track separately Rear are inside the front

IX. Recovery of Tire Track Evidence The procedure for recovery and processing of tire impression and/or track evidence includes: Photographs and Documentation Casting Comparison to known standard or source tire

a. Photographs and documentation First general crime scene photos are taken from various angles Diagrams and written notes describe the number of tracks, track width, relative positions, surrounding area, and direction of travel

Finally, examination photographs are made for identification of tread design. Longer impressions should include overlap

b. Casting Casts offer the best physical evidence for later comparison Shows 3-D features, contours, uneven qualities To allow examination of the noise treatment of a tire, a long cast must be recovered Any impression 4ft of less is always cast Dual tire assembly is always cast as a single unit

c. Comparison to a Known Standard Tire tread examinations compare the tire impressions recovered from scene with tires taken from a known vehicle Two categories of tires: Suspect - Vehicle of suspect Elimination - Vehicles of police, ambulance, etc

REMEMBER! RECOVERY Tire impressions must be: Photographed from all angles with and without measurement tool (ruler) Cast – a 3 foot impression requires 15-25 pounds of dental stone Measured – width, length and depth Direction of travel noted Impressions made if possible, and Pictures of the source (tire) must be included for comparison

REMEMBER! COMPARISONS Tire tread examinations compare the tire impressions recovered from scene with tires taken from a known vehicle Two categories of tires: Suspect - Vehicle of suspect Elimination - Vehicles of police, ambulance, etc All tires should be seized from suspect vehicle for comparison

REMEMBER! COMPARISONS Forensic examination begins with visual comparison and elimination of tires which do not match impression Forensic examination continues with full circumference test impressions Impressions are superimposed on known impression over cast or original tire

Dental Impressions

Forensic Odontology Forensic Odontology is the application of dentistry in legal proceedings deriving from ANY evidence that pertains to teeth.

Why Teeth? Every human body ages in a similar manner, the teeth also follow a semi-standardized pattern. These quantitative measurements help establish relative age of person. Each human has an individual set of teeth which can be traced back to established dental records to find missing individuals. Teeth is made of enamel (hardest tissue of the body) so it can withstand trauma (decomposition, heat degradation, water immersion, and desiccation) better than other tissues in body. Teeth are a source of DNA: dental pulp or a crushed tooth can provide nuclear or mitochondrial DNA that to help identify a person.

Who practices Forensic Odontology and what do they do? Forensic Odontologists Must have DDS degree Should have specialized training in the field through lectures (not required) Forensic dentists help: Identify human remains (individual and mass) Analyze bite marks Bite marks are compared to known teeth molds to find origin of bite injuries Estimate age of the victim and perpetrator Trace dental malpractice Top: Forensic Odontologist analyzing animal teeth for comparison. Side: Seal for American Board of Forensic Odontology.

History of Forensic Odontology 66AD – First body identified using teeth Lollia Paulina Revolutionary War Paul Revere was the first forensic dentist in the United States because he identified fallen revolutionary soldiers. 1849 – Mass deaths at Vienna Opera House Fire Dental evidence is first admitted into court system in US

Organizations of Forensic Odontology Bureau of Legal Dentistry (BOLD) American Board of Forensic Odontology (ABFO) International Organization for Forensic Odonto-Stomatology (IOFOS)

Hardest part of body attached TO jaws Hardest part of body attached TO jaws. IT serves to help digest food, act as a defense mechanism, etc. teeth are made of a crown with enamel surrounding a pulp. Teeth

Teeth Basics Approximately 32 teeth in adult mouth Four types of teeth: Molars Premolars Canine Incisors Teeth differ in: Size Shape Root type Types of teeth. Left to right: Incisor, Canine, Premolar, molar.

Teeth through the years Childhood Adulthood Primary teeth sprout from milk buds and are temporary. Once they fall out, permanent teeth as seen on the other side appear. Permanent adult teeth come in when primary teeth fall out; they are permanent because they establish roots inside the gums. Third molar come in around the mid teenage years.

Standard Teeth Development for Age Determination

Individual Characteristics Size of tooth Shape of tooth Shape of root Placement of tooth Quantity of teeth Combinations of dental work done: Crowns Extractions Bridge Fillings Root canals Various dental work

Analyzing Teeth The Universal System Teeth are given a specific number. (Primary teeth are given specific capital letter) Any dental work done on surface is noted Sheets kept on dental file forever. When person is missing, files are transferred to the missing person’s office

Identification Individual Identification Mass Identification Postmortem description is generated X rays and radiographs Positive identification is compared to ante-mortem data Negative identification, a biological profile is generated Same process is used as individual identification Organization is crucial Family is asked to come identify the body, and narrow down the pool of victims.

Various Teeth Found

Bite Marks Impressions from teeth found on skin or items left at a scene. Usually outline teeth placement.

Where are bite marks found? Impressions left on food, skin or other items left at a scene. Porous surfaces that absorb the impact enough to make an impression Impressions vary Depending on the pressure applied, the impression will show accordingly. The more pressure there is, the more detail to the bite.

Analyzing bite marks Bite marks are photographed with a scale Bite marks on skin are taken over repeated intervals Casts of impression are taken Impression traced onto transparencies Casts of suspects teeth are taken Comparison between suspect cast and bite mark

Various Bite Marks

Computer Odontology Automatic dental code matching OdontoSearch Bites are run through the computer to find a match OdontoSearch Compare a data base of missing peoples, felons, government workers Automatic dental identification system A few minutes will produce a list of people who have the same dental code number 3D Bite mark analysis 3D scans of dental casts are used to generate overlays using various pressure and deviation. The overlays are compared with the photograph of the bite marks.

Footwear Impressions

Forensic Significance of Footwear Impressions Whether on hard or soft surfaces, the direct physical contact between the shoe and the substrate (surface) results in a transfer of class and individual characteristics from the shoe to the impression it leaves Two-Dimensional Impression Three-Dimensional impression

Two-Dimensional Impressions As people walk about different they can acquire dust, dirt, residues, grease, oil, blood, and moisture onto shoes The shoes then deposit these materials back onto other surfaces they subsequently track over

Three-Dimensional Impressions Walking over surfaces such as sand, soil, or snow, they may cause permanent deformation of that surface

Class and Individual Characteristics Class and individual characteristics are examined to determine if a specific item of footwear made the questioned crime scene impression, or if that item can be eliminated.

Detection and Recovery of 2-Dimensional Footwear Impressions Electrostatic Lifting-utilizes high-voltage power source to create a static electrical charge that allows the transfer of a dust impression from the surface to a special black lifting film (mylar) Adhesive or Gelatin Lifting- the impression may be enhanced with fingerprint powder and lifted with a gelatin or adhesive lift.

Detection and Recovery of 2-Dimensional Footwear Impressions Prints in blood Chemical enhancement Can still obtain DNA results Faint & Diluted Bloodstain

Detection and Recovery of 3-Dimensional Footwear Impressions All three-dimensional impressions should be cast with dental stone. Dental stone is like plaster but sets much harder and has a higher compressive strength. Snow?

What About Impressions in Snow ?

Application of Snow Print Wax Casting with dental stone Collect & submit Cast to lab Inscribe case info & initials

Investigative Info Information Footwear Impressions may provide Identification of Footwear- class and individual characteristics Elimination of Footwear- Participation in the Crime- Location of Impression Rebuttal or Confirmation of Suspects Alibis- Determination of Shoe Brand- Linking scenes of Crime- Shoe Size- Association with other evidence- Gait Characteristics- Tracking-