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Impression Evidence II

Impression Evidence II. 3D Impressions. 3-D Impressions Impressed Evidence. Typically found in exterior surfaces Shoe deforms surface Sand/soil/snow – other soft surfacesCharacteristics Vary widely Shallow or deep Quality varies Can have great detail or none.

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Impression Evidence II

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  1. Impression Evidence II

  2. 3D Impressions

  3. 3-D Impressions Impressed Evidence • Typically found in exterior surfaces • Shoe deforms surface • Sand/soil/snow – other soft surfacesCharacteristics • Vary widely • Shallow or deep • Quality varies • Can have great detail or none

  4. 3-D ImpressionsValue of 3D Impressions • Impressions with sufficient detail can be associated with a specific item of footwear • Impressions in clay-based soil • Can retain great detail • Impressions in sand & small rocks • Little detail • Dry packed snow • Greater detail than wet, melting snow

  5. Collecting 3D Impression Evidence Sequence • Documentation • Sketching • Give lab knowledge where occurred @ scene • Lab can recreate as closely as possible to original • Differences in how recreated in lab v scene can affect making proper match • Field notes • Photography • Necessary for court presentation • Casting • Lifting

  6. Collecting 3D Impression Evidence Sequence • Most impression evidence has 3D characteristics … surface topography. • For forensic purposes, 3D impressions have depth in addition to length and width and commonly found outdoors in a soft or malleable receiving surface such as soil, sand or snow. • The quality (detail) varies with, • The receiving surface’s malleability, texture and composition. • The detail present in the source origin. • The mode by which the impression was transferred to the surface. • The affects of weather: temperature, rain and snow.

  7. Collecting 3D Impression Evidence Sequence • The scene investigator has no control over how the impression was generated or its clarity. • Responsibility: capture detail as completely and as clearly as possible. • Two activities: 1. Photography and 2. Casting. • Casting defined: • “the filling of a three-dimensional footwear impression with a material that will acquire and retain the characteristics that were left in that impression by the footwear.” • Each archiving technique complements the other • Photography and casting are not an either or decision. Both are critical and both must be done in order to properly archive the impressions.

  8. Lifting & Preserving 3D Footwear Impression Evidence

  9. What to Cast Indented (Impressed) Dry Impressions Wet, 2D Prints on Concrete Impressions in Snow Impressions Covered by Water

  10. Photography -v- Casting

  11. Casting Footwear ImpressionsCharacteristics of Forensic Quality Casting Material • Produce very fine detail • Flow easily into impression • Cleaned without loss of detail • Easily obtained with consistent quality & properties • Easily mixed – not require special equipment • Set in reasonable time • Unlimited shelf life

  12. Quality of Casts • Receiving surface malleability, • texture & composition • Sand • Clay • Loamy soil • Detail present in the impression • Mode by which impression transferred to the surface • Mechanics of making the impression • Effects of weather: • Temperature • Rain/snow • Wind

  13. Casting Gypsum manufacturing processes CaSO4-2H2O 110-130 Deg C Gypsum Calcium Sulfate Dihydrate (CaSO4)2-H2O 130-200 Deg C Plaster Calcium Sulfate Beta-hemihydrate CaSO4 200-1000 Deg C Stone Calcium Sulfate Alpha-hemihydrate Open Oven Autoclave Pressure Steam Plaster of Paris Requires more water Irregular Crystals & Porous Consistency > 50 Dental Stone Requires less water Uniform Crystals Dense Crystals Consistency < 50

  14. Choosing Dental Stone Several kinds of dental stone … always check the compression strength measured in psi (pounds per square inch).

  15. Casting Footwear ImpressionsGypsum Consistency vs Compressive Strength (psi) W:P – The quantity of water (by wt.) per quantity of powder (by wt.) A “30 Consistency” means – 30 parts of water/100 parts powder Higher the consistency – longer setting times – lower strength - softer

  16. Mixing Merlin's Magic • Merlin's Magic: Special type of casting material. • Made to pour into molds easily with very few air bubbles. • Mix differently than for regular plaster. Below are instructions to mix up enough plaster to fill one regular size mold. First you need to make a measuring cup that can be reused. http://www.hirstarts.com/casting/dental.html

  17. Procedure for Merlin’s Magic • Need two disposable plastic cups -nested. • Pour 2 ounces (60 ml) of water into the top cup and place a black mark on the outside of the bottom cup where the water line is. • Place an additional 2.5 ounces of water into the cup (for a total of 4.5 ounces or 135 ml). • Place another black mark on the outer cup at the water line. • Remove the inner cup and you have a reusable measuring cup. Here is how you mix the plaster

  18. Insert a new cup into your measuring cup. • Pour in water until it reaches the first line. • Carefully shake in the powder until the mixture reaches the second line. The powder must be absorbed into the water before you can determine if the second line is reached. • Remove the inner cup, mix up the plaster and pour it into your mold. • Mixing by weight, • Use table @ right. Need scale to measure the weight of the powder. • "ounces" shown here are a liquid measurement (not weight). • Mixing instructions on the package of Merlin's Magic will be different. • Their instructions are used for dental castings, which use a vibrator to shake thicker plaster into their dental molds, which can give mix that is too thick to pour into a mold.

  19. Casting Using Dental Stone

  20. Photographing the Impression Proper positioning of scales Positioning of Retainer

  21. Placing the casting frame in place Mixing water (3/4 cup/lb stone) and dental stone Pouring mixture onto impression

  22. Curing the cast Allow to sit 30-40 minutes before lifting Do not remove adhering soil • Final cast • Allow to cure up 24-48 hours • Carefully remove soil • Save Soil for comparisons

  23. CastingUnderwater Impressions • Drain or remove excess water – Good – BUT - Not Necessary • Pipette or syringe • Carefully Absorb with paper towel • Pour casting material as usual • If water can’t be removed? • Frame the impression • Sift dry casting powder gently into water above impression • Allow to fall to bottom • Sift until 1” of powder covers the area • Powder builds up & saturated with powder • Use additional dental stone slurry to fill the framed area • Will settle into the water later & into impression – cover entire impression • Allow to set for at least 1 hour

  24. Casting in Snow Casting Procedure • Spray Impression with Snow Print Wax or Dust with Snow Print Powder • 2-3 layers • Allow to dry for 2-5 minutes between applications • Slowly Add slightly cooled dental stone • Cooled dental stone minimizes melting the snow • Non-Casting Procedure • Auto primer spray paint before Snow Print • Better contrast for Photographs • Photos critical • Can’t directly cast with primer paint • Many snow prints not cast

  25. Snow Casting Procedure • Spray the impression lightly with the Snow Print Wax at an angle in order to highlight the raised areas of the impression. • Do not cover the entire area of the impression. This is the best time to photograph the sprayed impression. • Do not hold the spray too close to the impression because the blast from the aerosol can damage the impression’s detail. • Spray the impression with 2 or 3 more applications, ensuring that the entire impression is covered in wax. A properly sprayed impression will not reveal much detail when viewed from above. • The red (or other colored sprays) attracts heat: • Shield the impression from the sun. • Allow the wax mold to dry for approximately 5-10 minutes. • Prepare a dental stone slurry and allow it to sit longer than usual so that when the slurry begins to harden, the heat generated will not melt the impression. • When the cast is hardening, scratch initials and date into the cast. • Allow the impression to sit for approximately 60 minutes before lifting. • After lifting, immediately photograph the cast. • Snow print casts are fragile, and the wax molding is easily destroyed. Keep the cast away from sunlight. If melting occurs, cast detail may

  26. 3D Scanning Snow Print Wax Casting with plaster 3D surface scanning GOM ATOS II system (Gesellschaft fu¨r Optische Messtechnik mbH, Braunschweig, Germany). 3D model of the sole http://cs.iupui.edu/~tuceryan/pdf-repository/Buck2007.pdf

  27. Packaging Casts • Allow cast to dry for 24 hours or longer • Do not attempt to remove soil or clean until cured • Will destroy impression • Soil used for comparison purposes • Loosely & individually wrapped in paper or paper bag • Do not wrap in tight plastic • Place wrapped cast in cardboard box & tape seal • Place in shock absorbent or porous packaging material

  28. Illinois State Police Packaging Procedure for Cast Impressions • Identification: • Before cast hardens, place CSI or investigator’s initials, date and case & number on back side of cast. • Amount Desired: Standard -Evidence - Up to 2 ft. • Preservation: • Use mesh reinforcing and let dry 24 hours before putting in package. • Wrapping & Packing: • Surround with packing material in box too prevent shifting or • breakage. Avoid sealing in plastic bags. • Miscellaneous: • Dental stone is the preferred casting material. Take photos of impressions • before casting. Mark package FRAGILE. Do not clean. Do not use twigs for reinforcement. http://www.isp.state.il.us/docs/6-420.pdf

  29. Impression Evidence On-Scene Overview

  30. [1] Adapted from Hilderbrand, Dwane S. Footwear, The Missed Evidence, Skaggs Publishing 1999, pages 61-62.

  31. Exemplar Impressions

  32. Exemplar Footwear Impressions • Many people leave impressions @ scene • Categorize designs of shoes • Victims • Witnesses • Medical personnel • Other innocent people • Officers • Suspects • Known impressions made • Specialty impression materials available • Biofoam http://site.utah.gov/dps/impressions-fw-evidencecollection_000.htm

  33. Gellifter Inkless Lifter http://site.utah.gov/dps/impressions-fw-evidencecollection_000.htm

  34. Forensic Footwear Databases • TreadMark™ • The number of shoe prints at a crime scene can be so large that the process of impression recovery becomes very time-consuming. • Commercial product using four parameters—pattern, size, damage, and wear—to identify individual outsole impressions. • Compared with shoe print data from two sources: suspects in custody and crime scenes. • A match could yield the name, date of birth, criminal record number, places of interest, and similar offenses for possible suspects. • How does TreadMark™ work? • Impressions from crime scene obtained using photograph, gel lift, dust lift, and adhesive lift. • Input directly into the analytical system by high-resolution digital imaging. Same procedure used with impression of a suspect’s shoe print: • Operator measures, analyzes, and compares crime-scene and suspect images. • Both image sources can be searched within themselves and against each other, allowing such images to be transmitted to other users. • www.csiequipment.com/systems.aspxExit Notice.

  35. SoleMate • Commercial database contains information—manufacturer, date of market release, an image or offset print of the sole, and pictorial images of the uppers—for more than 12,000 sports, work, and casual shoes. • Sold on DVD, updated and distributed to subscribers every 3 months. • Limitation is that different manufacturers often use the same sole unit. Therefore, it may be difficult to determine the exact make and model of a shoe. The software links such records, however, so that all footwear that might match a crime-scene print can be considered. • How does SoleMate work? • The pattern of an unidentified shoe print is assigned a set of codes to isolate basic features, such as circles, diamonds, zigzags, curves, and blocks. Options, with variations, are presented pictorially, allows investigator to code features that best match the shoe print. • These codes form the database search, with results presented in descending order of pattern correlation. • Foster & Freeman USA Inc., at 888-445-5048.

  36. TreadMate • Maintained by the same United Kingdom company that markets SoleMate, this database contains information: • 5,000 vehicle tires and tire tread patterns, • Manufacturer, • Date of market release, • Pictorial image, • Pattern features. • Because manufacturers sometimes use the same tread, it may be difficult to find the exact make and model match of a tire. In these cases, records are linked so that all tires that might match a crime-scene tire mark may be considered. • How does TreadMate work? • The pattern of an unidentified tire mark is assigned a set of codes for pattern features, such as waves, lines, diamonds, zigzags, curves, and blocks, which then form the basis of the database search. Results are presented in descending order of correlation. • Foster & Freeman USA Inc., at 888-445-5048 or usoffice@fosterfreeman.com.

  37. Tire Print Evidence Evidence Often Overlooked

  38. Vehicle-Involved Scenes • Vehicle-involved scenes run the gamut of scene types: homicides, sexual assaults, burglaries, drive-by shootings, terrorist events, etc. • Identifying vehicle should be a critical aspect of any on-scene investigation. • In typical homicide investigation, investigators must consider the possibility that specific categories of physical evidence related to the crime are present. • Hit and run crimes, whether vehicle-vehicle, vehicle-person, vehicle-other object, involve vehicles that leave the scene. • In these crimes, damage creates physical evidence • Evidence could prove the culprit vehicle was at the scene; • This evidence should be collectable.

  39. The following article from the New York Daily News is such an example[1]. In this case, the suspect and his vehicle were found. The NYPD crime scene unit had the responsibility of working the car to prove it was the vehicle that struck the victim.

  40. Case Example Kidnapping • Hypothetical - Kidnapping • Involves a vehicle for transport • Critical to find physical evidence that the child had been inside the car, • Reality: Such evidence may not be present or had been removed. • The abducted child case. • No evidence found inside the suspect vehicle proving the child there … • Must consider other, indirect, avenues to move investigation forward. • The abductor vehicle had been at the scene. • Success includes thorough investigation of the outside where the vehicle might have been parked • Physical evidence collected and scene archived. • One example of physical evidence vehicles leave behind is tire track impressions.

  41. Tire Track Impression Evidence • Evidence Often Overlooked • Footwear Impression: • Dealt with locating, enhancing, photographing, etc, footwear impression evidence, • Much of that discussion is applicable to tire track evidence as well. • Similarities with Footwear Impressions • Tire track evidence: • Classified as two-dimension (2D) or three-dimension (3D). • Commonly in dust or are otherwise contaminated 2D impressions or impressions in a soft surface. • Considered Class or individualizing: • Physical characteristics needed for meaningful criminalistic-quality comparisons • Former provides information about the tread design • Latter provides information imbedded into the tread of the tire from daily usage.

  42. Footwear & Tire Track Differences Their Intrinsic Forensic Values • Provides evidence of the individual (shoe impressions) or the vehicle (tire impressions) being at the scene, • For tire tracks, suggests the individual vehicle was used in the crime. • Tire track impressions geared to identify vehicle … not the person, • Although the person might have been driving the vehicle.

  43. How Important is Scene Evidence? • Identifying specific vehicle requires recovering it and making direct comparisons with physical evidence from scene • Scene data allows investigators and laboratory analysts to narrow the search among universe of vehicles. • Until suspect vehicle is located and impounded, all scene data must be archived, collected and preserved. • Determining which tire tracks to photograph, enhance and or cast is critical

  44. Critical Vehicle InformationCrime Scene Procedures Direction of travel Relationship of impressions @ scene to arrangement of tires on suspect vehicle Position of front of vehicle Which impressions made by front & rear tires Which impressions to photo/cast Locations where vehicle track measurements will be recorded Other relevant evidence Footwear impressions Fluid spills • How vehicle was maneuvered? • Vehicle characteristics • Stance • Track measurements • Wheelbase • Tread wear indicators • Wear bars • No. vehicles & no. occupants • Were objects loaded or unloaded?

  45. On-Scene Considerations

  46. Success At the Scene One Shot at It • Unknown: • Whether something seemingly unimportant and ignored will be important as evidence AND suddenly plays a prominent role in the investigation. • Consider everything at vehicle-involved scenes as potentially probative. • Misperception that tire track impressions have little forensic or investigative value. • General scene investigative principles apply equally to vehicle-involved scenes; • Management, archiving, searching, etc, are an integral aspect of the investigation.

  47. Crime Scene Procedures Secure the area Tire prints protected Obtain information Case information Vehicle information Scene information Establish safe path to view evidence Archive Collect/package/preserve evidence

  48. Management • Should employ guidelines previously discussed • While these principles are inviolate • Unique characteristics for vehicle-involved scenes. • Specifically, identifying, archiving, characterizing and preserving the physical evidence associated with identifying a suspect vehicle. • Investigative Questions • Archiving • Sketching and critical on-scene measurements • Vehicle information • Suspect information • Reconstruction

  49. Archiving

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