Presentation on theme: "WARMUP!!!!! When I graduate from high school I want to……."— Presentation transcript:
WARMUP!!!!! When I graduate from high school I want to…….
UNIT 3 IMPRESSION EVIDENCE
What Causes Impression Evidence???? When one object presses hard against another object and leaves an indentation or print
What kind of impression evidence can you think of?
Best way to view an impression… Making a cast!!!! For example, a trip to the dentist……
You all have had one of these done before??
What happens?? An impression is made…. This would be your tire tracks, foot prints, etc Then it is filled with a plaster that is mixed up This is allowed to dry and it pulled out of the impression THEN YOU END UP WITH…..
YOUR MOLD/ CAST
TODAYS FOCUS TIRE TRACKS!!!!!!
Why is tire track evidence so hard????? Because there are so many cars that are similar!!!!
Police have to go in and find that specific car that matches those tracks, but that’s a big job to narrow down.
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
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
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
So what did we learn already?? Tire tracks would be considered what type of evidence??? CLASS!!!!
Tire tracks can be individualized how???? Wear marks Nails in tires PatchingGravel Skidding caused by sudden stops
Forensic Science Activity T. Trimpe 2007
Tire Track Lab Your group will need to document the tread patterns for each vehicle. Step 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.
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. Tire Track Challenge
WARMUP Why are tire tracks so hard to trace to a source? What would make them easier to link to a suspect’s vehicle?
UNIT 3: DAY 2 FOOT PRINTS!!!!!
What are footprints?? Impression left in the Earth after someone walks on it.
What can footprints tell us about a crime??? Direction of approach and departure Point of entry and exit Mode of entry Sequence of events that took place
How long can footprints last? Couple of minutes to hundred of years….. So what type of evidence can a footprint be?? TRANSIENT!!!!!
Footprints Can Be 2D or 3D
Things Prosecution Looks for When Examining Footprints The walk or gait of the person who left the footprints, Sole or heel indents Cuts or the tread of a shoe, and Other signs of wear associated with a shoe.
Investigators can determine a person’s size and the speed (Running or walking) they were going
Gait A manner of walking or moving on foot. It can be as individualized as your personality.
Three 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 scene An expert witness that can testify to the connection between the two beyond a reasonable doubt. expert witnessexpert witness
LAB FOOTPRINT CASTING MEASUREMENTS
DIRECTIONS Meaure length of shoe you’re wearing by standing on ruler Have someone measure your height Collect similar data from your classmates Plot height (y axis) against shoe length (x axis). One set for males, one set for females
Questions to Consider Is there a correlation between shoe length and height? How could investigators utilize this information?
WARMUP What steps would a detective take to determine who a suspect is based on footprints?
UNIT 3: DAY 3 Tool Marks
What causes tool marks?? The use of a tool against a usually softer object Ex: screwdriver used to open a window is pressed into the softer windowsill, leaving a mark
How can tools be used in a crime? Stabbing or hitting another individual Break into things
Features to Analyze Dimensions of the impression Dimensions of the impression Ridges or striation patterns Ridges or striation patterns Defects, such as nicks and chips Defects, such as nicks and chips Paint chips or metal shards left on a tool Paint chips or metal shards left on a tool
Places and Surfaces Where Tools Might Be Used wire, chainsdoor and window framessections of sheet metal safety-deposit boxes, human bone or cartilage padlocks, doorknobsbolts and locksand a variety of other materials
Main Tools Used At a Crime Scene bolt cutters screwdrivers and chisels scissors knives and box cutters pliers and wrenches crowbars tire irons saws, knives Read more at Suite101: Toolmarks at a Crime Scene: Forensic Criminal Investigations can Link Toolmarks to Tools | Suite101.com at a Crime Scene: Forensic Criminal Investigations can Link Toolmarks to Tools | Suite101.com
Tools Can Be Classified Two Ways ImpressionScratches
Class and Individualized Characteristics Class- Size and shape of tool. Individualized- As tool is used more it becomes worn and damaged
Forensic Science Activity T. Trimpe 2007
Tool Marks Lab Goal: Your group will need to examine and document the tool marks made by each of the tools. 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 impression Ridges or striation patterns Defects, such as nicks and chips Paint chips or metal shards left on a tool Image:
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! Tool Mark Challenge
WARMUP How can a tool mark be individualized?
UNIT 3: DAY 4 BITE MARKS
When are bite marks most often found?? Assault or sexual attack Victims of domestic violence
EVERYBODY HAS DIFFERENT TEETH SHAPESWIDTHARRANGEMENT
What Else Can Differentiate Teeth? ChipsFillingsCrownsCaps
Features to Analyze Type of bite mark (animal or human) Characteristics of the teeth Color of the area to estimate how long it’s been Swab body fluids for DNA
Forensic Odontology branch of forensic science that deals with the handling, examination, and presentation of dental evidence in court
Why Teeth?? They can withstand fire, harsh conditions, etc. X-RAY records can identify an individual involved in a gruesome murder where body is no longer recognizable
Wayne Boden: “The Vampire Rapist”
Bite Marks Were One Main Piece of Evidence Used to Convict Ted Bundy
Presentation developed by T. Trimpe 2010
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. Part 1: Make an Impression Width Depth Maxilla Mandible Maxilla Mandible
1 – 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. Part 2: Tasty Testing Type of CandyQualityObservations
WARMUP What did you learn from the bite mark activity yesterday?