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

RECOVERYTire 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

COMPARISONSTire 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, etc

All tires should be seized from suspect vehicle for comparison

COMPARISONSForensic 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

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 indentsCuts or the tread of a shoe, andOther signs of wear associated with a shoe.

Investigators can determine a person’s size and the speed (Running or walking) they were going

GaitA 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 sceneAn expert witness that can testify to the connection between the two beyond a reasonable doubt.

http://www.youtube.com/watch?v=qlmZZoLGMpM

LAB

FOOTPRINT CASTING

MEASUREMENTS

DIRECTIONSMeaure length of shoe you’re wearing by standing on rulerHave 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

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 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 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 AnalyzeType 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?