11What happens??An impression is made…. This would be your tire tracks, foot prints, etcThen it is filled with a plaster that is mixed upThis is allowed to dry and it pulled out of the impressionTHEN YOU END UP WITH…..
19RECOVERY Tire impressions must be: Photographed from all angles with and without measurement tool (ruler)Cast – a 3 foot impression requires pounds of dental stoneMeasured – width, length and depthDirection of travel notedImpressions made if possible, andPictures of the source (tire) must be included for comparison
20COMPARISONSTire tread examinations compare the tire impressions recovered from scene with tires taken from a known vehicleTwo categories of tires:Suspect - Vehicle of suspectElimination - Vehicles of police, ambulance, etcAll tires should be seized from suspect vehicle for comparison
21COMPARISONSForensic examination begins with visual comparison and elimination of tires which do not match impressionForensic examination continues with full circumference test impressionsImpressions are superimposed on known impression over cast or original tire
22So what did we learn already?? Tire tracks would be considered what type of evidence???CLASS!!!!
23Tire tracks can be individualized how???? Wear marksNails in tiresPatchingGravelSkidding caused by sudden stops
25Your group will need to document the tread patterns for each vehicle. Tire Track LabStep 1: Get a large piece of white paper from your teacher, an ink pad, paper towels, and a ruler. You will also need a pen or pencil.Step 2: Gently roll a car over the ink pad several times to cover all the sides of the tires.Step 3: Gently roll the car on the white paper for a length of 5-6” and label the tracks with the car’s letter.Caution: You will want to apply enough pressure to get a good impression, but not too hard that you cause damage to the vehicle, its tires, or the ink pad.Step 4: Roll the car on a piece of paper towel to remove excess ink and then pass it along to another group.Step 5: Analyze the tire tracks to identify unique characteristics, such as blank spots, evidence of tire wear, width of the track, etc. Use a highlighter to mark each characteristic you find.
26Ready? Set? GO! Tire Track Challenge Work with your investigative team to identify each set of tracks shown on your worksheet.Compare the tracks you made earlier and match them to the suspect tracks on the worksheet. Once you have identified all the cars, have your answers checked by your teacher.Ready?Set?GO!
27WARMUPWhy are tire tracks so hard to trace to a source? What would make them easier to link to a suspect’s vehicle?
33Things Prosecution Looks for When Examining Footprints The walk or gait of the person who left the footprints,Sole or heel indentsCuts or the tread of a shoe, andOther signs of wear associated with a shoe.
34Investigators can determine a person’s size and the speed (Running or walking) they were going
35GaitA manner of walking or moving on foot. It can be as individualized as your personality.
36Three things are needed to actually use footprints to convict someone…. A photography, plater mold, or print of the original and un-tainted footprint,The actual shoe or mold of a foot that belongs to the defendant and the prosecution believes matches the one at the crime sceneAn expert witness that can testify to the connection between the two beyond a reasonable doubt.
40DIRECTIONS Meaure length of shoe you’re wearing by standing on ruler Have someone measure your heightCollect similar data from your classmatesPlot height (y axis) against shoe length (x axis). One set for males, one set for females
41Questions to ConsiderIs there a correlation between shoe length and height?How could investigators utilize this information?
42WARMUPWhat steps would a detective take to determine who a suspect is based on footprints?
46How can tools be used in a crime? Stabbing or hitting another individualBreak into things
47Features to Analyze Dimensions of the impression Ridges or striation patternsDefects, such as nicks and chipsPaint chips or metal shards left on a tool
48Places and Surfaces Where Tools Might Be Used wire,chainsdoor and windowframessections of sheet metalsafety-deposit boxes,human bone or cartilagepadlocks, doorknobsbolts and locksand a variety of other materials
49Main Tools Used At a Crime Scene bolt cuttersscrewdrivers and chiselsscissorsknives and box cutterspliers and wrenchescrowbars tire ironssaws, knivesRead more at Suite101: Toolmarks at a Crime Scene: Forensic Criminal Investigations can Link Toolmarks to Tools | Suite101.com
50Tools Can Be Classified Two Ways ImpressionScratches
51Class and Individualized Characteristics Class- Size and shape of tool.Individualized- As tool is used more it becomes worn and damaged
52Forensic Science Activity Tool Mark ChallengeForensic Science ActivityT. Trimpe 2007
53Goal: Your group will need to examine and document the tool marks made by each of the tools. Tool Marks Lab At each station, you will need to: 1 – To prepare for the lab, roll the modeling clay into a flat circle that fits inside the plastic plate. Make several impressions of each tool in your slab of modeling clay.2 – Use the ruler to record the measurements for each tool and its impression surfaces.3 – Document any unique characteristics you notice on each tool or its impression. Write your observations on your worksheet.4 – After you have documents both of the tools at that station, roll the clay into a ball to prepare for the next group and wait until it's time to rotate to the next station.Features to analyze:Dimensions of the impressionRidges or striation patternsDefects, such as nicks and chipsPaint chips or metal shards left on a tool Image:
54On your mark? Get set? Go! Tool Mark Challenge Work with your investigative team to identify the crime scene tools.Compare the tool marks you made earlier and match them to the crime scene tools. Once you have identified all the tools, have your answers checked by your teacher. Keep trying until you have them all correct!On your mark?Get set?Go!
55How can a tool mark be individualized? WARMUPHow can a tool mark be individualized?
64Bite Marks Were One Main Piece of Evidence Used to Convict Ted Bundy
65Bite Mark Identification Presentation developed by T. Trimpe 2010
66Part 1: Make an Impression 1 – Fold the Styrofoam plate in half.2 – Label one side MAXILLA and the other MANDIBLE.3 – Gently bite down on the plate to leave your bite mark impression.4 – Place a sheet of the plastic film over the impression and use a permanent marker to recreate the pattern to match that of your bite mark.5 – Use a ruler to make the measurements shown and record in the table below along with any notes regarding unique characteristics you observe in the teeth.MaxillaMandibleDepthMaxillaWidthMandible
67Part 2: Tasty Testing1 – Use the various pieces of candy to make bite mark impressions.2 – Record your observations for each one as well as provide a rating of the impression quality using poor, fair, or good.Type of CandyQualityObservations
68What did you learn from the bite mark activity yesterday? WARMUPWhat did you learn from the bite mark activity yesterday?