CRIME SCENE PHOTOGRAPHY IMPRESSION EVIDENCE BY PROFESSOR MIKE WIEHE Collection and Preservation of Evidence

O BJECTIVES The student will be able to Describe methods for locating and preserving impression evidence at a crime scene Demonstrate proper procedures for photographing impression evidence Demonstrate procedures for casting impression evidence Describe methods for lifting impression evidence 2 Impression Evidence

I MPRESSION E VIDENCE Shoeprint and tire impression evidence Criminals rarely take steps to cover shoe or tire impressions Hasty or disorganized search can result in destruction of this fragile evidence Oblique lighting helps locate shoeprints on surfaces 3 Impression Evidence

I MPRESSION E VIDENCE Shoeprint and tire impression evidence Oblique lighting helps locate shoeprints in dust Photograph prior to lifting 4 Impression Evidence

I MPRESSION E VIDENCE Lift dust shoeprint with rubber lifts or electrostatic dust print lifter 5 Impression Evidence

I MPRESSION E VIDENCE The electrostatic dust print lifter is used to electrically charge a metallic film, which is placed over dust print The electrostatic charge causes dust to adhere to the metallic film 6 Impression Evidence

I MPRESSION E VIDENCE The “lift film” is placed over the dust print DO NOT SLIDE IT INTO POSITION 7 Impression Evidence

I MPRESSION E VIDENCE A grounding strip is placed silver side down about 1-2 inches from place where lift film will be placed. Yellow ground wire is attached to this film. 8 Impression Evidence

I MPRESSION E VIDENCE Lift film should cling to surface beneath it Crackling sound may be heard 9 Impression Evidence

I MPRESSION E VIDENCE While maintaining electric charge, use roller to gently apply pressure on film to obtain maximum contact between film and the surface 10 Impression Evidence

I MPRESSION E VIDENCE Carefully remove film and turn it over Film is best packaged in a folder and taped in place 11 Impression Evidence

I MPRESSION E VIDENCE Photograph the impression as soon as possible Consider using oblique lighting to photograph the image 12 Impression Evidence

T IRE & S HOEPRINT E VIDENCE All impressions should be photographed (with and without scale) Then casted or lifted 13 Impression Evidence

P HOTOGRAPHY OF I MPRESSIONS Shoe Impressions First photo without scale with flash on camera Subsequent photos with scale and flash to the sides Ruler should be depressed into surface to same depth as impression Use black cape to create shadow 14 Impression Evidence

P HOTOGRAPHY OF I MPRESSIONS Tire Impressions Photo entire impression Overlap each previous photo Lay tape measure along entire track and include in photos 15 Impression Evidence

C ASTING Carefully remove loose debris Use a Q-tip dipped in oil to remove small debris Place form around impression if necessary (on an incline) 16 Impression Evidence

C ASTING Mix approximately 2 to 2-1/2 parts dental stone to 1 part water in a plastic zip-lock bag Mix until desired consistency by kneading the bag with your hand (pancake batter) 17 Impression Evidence

C ASTING Dental stone requires no reinforcement material Pour dental stone over a wide stick to the side of the impression NEVER pour directly onto the impression 18 Impression Evidence

C ASTING Mark your identifying information into back of cast before it completely hardens Allow cast to dry for 30 minutes before removing (depends on temperature) Do not attempt to clean cast Allow it to air dry 48 hours 19 Impression Evidence

I MPRESSIONS IN S NOW It is recommended that prior to lifting a footwear print in snow, spray impression with snow wax to reinforce print Let each layer dry briefly before applying next. Wax is usually colored Photograph colored impression prior to pouring dental stone 20 Impression Evidence

I MPRESSIONS IN S NOW Wax spray is applied in several thin layers Each wax layer needs several minutes to set Enough layers should be applied to establish and protect the impression Wax base will protect the impression from the heat of the casting material as it cures 21 Impression Evidence

S HOE I MPRESSION C ASTING 22 Impression Evidence

I MPRESSIONS IN S NOW To spray properly, wax spray must be kept warm It should not be too hot lest it melts the impression Old or cold wax spray may not function properly, resulting in uneven wax application and lower cast quality 23 Impression Evidence

S HOE I MPRESSION C ASTING 24 Impression Evidence

S HOE I MPRESSION C ASTING 25 Impression Evidence

S HOE I MPRESSION C ASTING 26 Impression Evidence

I MPRESSIONS IN S NOW Gently pour prepared dental stone into impression over the snow wax When dental stone is cool and hard, remove it from the impression The wax will adhere to the dental stone 27 Impression Evidence

S HOE I MPRESSION C ASTING 28 Impression Evidence

S HOE I MPRESSION C ASTING Leave the cast in place until hard Approximately minutes, depending on environmental conditions With a snow impression, cover casting material with a box or newspaper to help material retain its heat as it cures Do not freeze it before it cures 29 Impression Evidence

S HOE I MPRESSION C ASTING 30 Impression Evidence

S HOE I MPRESSIONS IN W ATER Mix 4 parts dental stone to 1 part water Create dam around impression to stop wave action Use a form Gently sprinkle dry dental stone over impression Allow excess dental stone to float away 31 Impression Evidence

S HOE I MPRESSIONS IN W ATER Gently pour mixed dental stone over paint stir stick onto impression Scratch identifying info on drying cast Allow it to set for minutes before removal 32 Impression Evidence

P ACKAGING C ASTS Ship casts to lab wrapped in shock absorbent, porous packaging material DO NOT wrap or place in plastic or it will mold 33 Impression Evidence

TOOL MARK IMPRESSIONS 34 Impression Evidence

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M IKROSIL C ASTING M ATERIAL For casting tool mark striations or lifting latent fingerprint impressions Mix 1 cm. Mikrosil to 1 cm. of hardener with wooden tongue depressor Mix from 30 seconds to 1 minute 36 Impression Evidence

M IKROSIL C ASTING M ATERIAL Apply with depressor Remove when dry 37 Impression Evidence

E XTRUDE C ASTING M ATERIAL Similar to Mikrosil PVS (Plilly Vinyl Serere) Contains casting material and hardener in one tube (no mixing required) Automatically mixes materials Apply to tool mark using application gun Let dry and remove 38 Impression Evidence

Q UESTIONS ? 39 Impression Evidence