1. The Impression that I get!

2. 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

3. 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

4. Tread Nomenclature and Sidewall Information

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

6. 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

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

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

10. 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

12. 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

13. 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

14. 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’

16. 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

18. 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

19. 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

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

21. 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

22. 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

23. REMEMBER! RECOVERY Tire impressions must be:
Photographed from all angles with and without measurement tool (ruler)
Cast – a 3 foot impression requires 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

24. 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

25. 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

26. Dental Impressions

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

28. 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.

29. 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.

30. 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

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

32. 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

33. 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.

34. 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.

35. Standard Teeth Development for Age Determination

36. 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

37. 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

38. 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.

39. Various Teeth Found

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

41. 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.

42. 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

43. Various Bite Marks

44. 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.

45. Footwear Impressions

46. 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

47. 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

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

49. 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.

50. 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.

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

52. 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?

53. What About Impressions in Snow ?

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

55. 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-