Impression Evidence Review

Flashcards for reviewing key concepts in impression evidence analysis.

What are the two main areas of analysis for impression evidence?

Crime scene analysis and laboratory analysis

What are some challenges faced by lab examiners when analyzing impression evidence?

Lack of information/misinformation, unlabeled photographs/casts, and confusing tracks.

What are class characteristics in impression evidence?

Size, shape, style, pattern design, manufacturing flaws (repeated).

What are accidental characteristics in impression evidence?

Cuts, tears, wear marks, manufacturing flaws (random).

What are the possible conclusions when dealing with impression evidence?

No comparative value, elimination, class characteristics only, positive individualization.

What should be done with suspect shoes during collection?

Always collect suspect shoes and remind the investigator to put the suspect in the shoes.

Why are inkless kits used in impression evidence collection?

For elimination purposes.

What are some crime scene challenges when it comes to impression evidence?

Lack of resources/time, lack of training, large scale scene, numerous tracks, confusing tracks.

Name the types of information that impression evidence can provide at a crime scene

Minimum # of suspects / vehicles, classification of footwear / tires / vehicle, manner that items were deposited, estimated time of event, support or rebut witness / suspect statements, point of entry/exit, actions of individuals / vehicles, direction of travel / orientation of vehicles, vehicle measurements.

What are some things to consider when searching for footwear impression evidence?

Not all impressions are visible, contamination doesn't mean prints can't be found, outdoor impressions must be processed quickly, consider the incident, tracks don't suddenly end, check under items, consider substrate and types of impressions.

What are lighting techniques used in impression evidence?

Existing/supplemental light, darken areas and use oblique light, alternate light source (ALS).

What chemical is used in searching for blood impressions?

Luminol (other commercial products).

How should objects containing impressions be packaged?

In a manner that prevents damage, preferably using cardboard (not plastic).

What are the key elements of examination quality photographs for impression evidence?

Tripod, camera plane parallel, proper lighting (external, natural, oblique), scale, ID tag, item designation, north arrow, tire position/direction.

What is the image inversion phenomenon?

An impression that appears to be raised but is actually depressed when the image is rotated 180 degrees.

What are methods for lifting impression evidence?

Electrostatic dust print lifter, dusting with fingerprint powder and using gel lifts.

What are 2-D and 3-D impressions

2-D has length and width, but no significant depth. 3-D has length, width, and depth.

What is the importance of pouring outside the track when casting?

Pour the mixture outside of the track at a point which will allow the mixture to flow into the depression.

Give an example of different types of casts

'Framed' cast and 'Pancake' cast

What is the use of snow print wax, auto body primer and Sulfur casting?

Casting in Snow

What are the two components for Item Designations?

Specific Item Number and Segment Number

Name the notes for Impression Evidence Documentation

Location, direction, amount, relationship, movement, transferred material, substrate

Name the Documentation Notes for Enhancement Techniques

Direction of Travel and Tire Position Determinations

Name the 3 Documentation techniques for Tire Tracks

Overall Photographs, Diagram with Track Evidence and Examination Quality Photographs

Name the characteristics for Absence of impressions

Relationship to other evidence, Absence of impressions and Track width

What is meant by Wheelbase?

Axle to axle

Define Circumstantial Factors

Sequencing of events and Witness/Suspect statements

List the components of Shoeprint Interpretation

Single and multiple tread designs