warmup!!!!! when i graduate from high school i want to……
TRANSCRIPT
WARMUP!!!!!
When I graduate from high school I want to…….
UNIT 3IMPRESSION 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?
Tire tracks
Footprints
BITE MARKS
TOOL MARKS
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.
Tire track evidence consists of….
Tire track widthWheelbase dimensionsTurning diameterRelative positions of turning tracks
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 stoneMeasured – width, length and depthDirection of travel noted Impressions made if possible, andPictures 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 suspectElimination - 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
Patching
Gravel
Skidding caused by sudden stops
Forensic Science Activity
http://pro.corbis.com/images/CB001940.jpg?size=572&uid={D27A89DF-00BB-4028-AA57-7A908AF0511D} T. Trimpe 2007 http://sciencespot.net
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 2FOOT 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.
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 3Tool 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
• Ridges or striation patterns
• Defects, such as nicks and chips
• 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 http://suite101.com/article/toolmarks-at-a-crime-scene-a41620#ixzz27FRzXMQS
Tools Can Be Classified Two Ways
Impression Scratches
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 http://sciencespot.net
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: http://www.maine.gov/dps/msp/criminal_investigation/crimelab/images/toolmarks1.jpg
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 4BITE MARKS
When are bite marks most often found??
Assault or sexual attack Victims of domestic violence
EVERYBODY HAS DIFFERENT TEETH
SHAPES
WIDTH
ARRANGEMENT
What Else Can Differentiate Teeth?
Chips
Fillings
Crowns
Caps
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
http://www.youtube.com/watch?v=HxQ1QFUGKqo
Presentation developed by T. Trimpe 2010 http://sciencespot.net
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
WidthDepth
http://forensicfact.files.wordpress.com/2008/05/cast_negative_resized_copy.jpg
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 Candy Quality Observations
WARMUP
What did you learn from the bite mark activity
yesterday?