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Transcript of Impression Evidence
A standard henry 10 print fingerprint card is used for collecting inked impressions of a subject's fingerprint's.
before fingerprinting, a subject must wash and dry hands completely to remove any contaminants or foreign particles that might prevent accurate ridge detail from being recorded.
both the officer obtaining the prints and the subject being printed should sign the fingerprint cards.
plain impressions: are used to verify that each of the individual rolled prints have been placed in the proper sequence of the top of the card.
Methods of Collection
Impression evidence can be collected in various ways, the most prominently used methods are generally 2-D & 3-D.
2-D: This type of impression is documented using photography. Some impressions may be dusted with fingerprint powder to be photographed or lifted with tape.
3-D: This type of impression can be documented using photography as well as by casting, which involves using dental stone or a similar material to preserve the impression of the
Shoe Print Evidence
Investigators analyze shoe prints to determine its type, size, and brand. They also look for individual characteristics, such as wear patterns and personal markings and damages.
Based on the quality of the impression, investigators may be able to determine a person’s speed as well as estimate the size of the person.
To identify the shoe, police analyze:
Tread patterns, size, and depth
Wear patterns caused by the way a person walks
Material defects or damage (nicks, cuts, etc.)
Trace materials, such as soil, tar, rocks, and paint
Tire Track Evidence
Tire tracks are usually found in road accident scenes or in the access and escape routes of other crime scenes. Tracks help investigators identify the vehicle. Investigators may make ink prints of a tire or plaster casts of a track. They will also take photographs that can later be used to prove a match.
Features to analyze:
Width & depth of the tread pattern
Unique characteristics due to the wear pattern or defects
What is Impression Evidence?
is a form of material used to retain or mirror the characteristics
of other objects that have been pressed against them. These impressions are created when something is pressed against another specific imprinting material with enough force to leave an exact replica of the item being imprinted on the material.
Included in this category are fingerprints, palmprints, nose/ear prints, toolmarks, footwear, tire and sometimes fabric impressions.
Impression Evidence Case:
Serial Arsonists in Alabama
The police use fingerprints to identify suspects by matching prints found at a crime scene with prints already in police files from a previous conviction.
The validity of fingerprint evidence is based upon two principles:
No two people have the same fingerprints
A person's fingerprint patterns never change.
Fingerprint experts use powders and chemicals to make such prints visible.
On two nights in February 2006, nine churches in Alabama were set on fire by arsonists. The damning piece of physical evidence that linked the suspects to each of the arson's were tire tracks that were found at all the crime scenes. Police tracked the unusual tire tracks to a tire dealership in Shelby County, Alabama. The dealership told police that the tires had been ordered by Shelley Cloyd for her Toyota 4Runner. After speaking to Mrs. Cloyd police learned that the primary driver of the car was her son, Matthew Cloyd. This impression evidence was used to place Matthew at the various crime scene and allowed investigators to uncover enough evidence to convict Matthew Cloyd and two other suspects of arson in December 2006.
Tool Mark Evidence
Defects or scratches may be left on a tool when it is made or used, which can be used to find matches between evidence at a crime scene and tools or objects found in the possession of a suspect.
Tool marks can be classified two ways:
Impressions – As a tool hits a softer surface, the shape of the tool and imperfections in its surface may be left behind as an impression.
Scratches – As a tool moves across a surface, it may leave ridges or striations behind.
Preserving Impression Evidence
Because of the short longevity of evidence, the first thing forensic investigators do when they come across impression evidence is preserve it.
Impression evidence is preserved using:
- 2-D impressions like fingerprints are often collected using a lifting machine or using photographs.
- 3-D impressions are collected using casts. The cast is poured into the impression, hardened, and removed.
By: Katherine Garrison
casting and lifting impressions
Impressions on surfaces have to be secured, protected, and collected.
challenge because of weather conditions.
Wet conditions dictate any changes in protocols.
What are ink impressions?
Footwear impressions make it possible to
determine the number of suspects and/or the paths taken to and from the crime.
These types of prints are very delicate and must be properly documented in the early stages of an investigation.
There are two forms of footwear evidedence
Where and how you display your camera can make a difference on the image you just took.
Images illustrate the importance of placing the scale at the correct depth relative to an impression; a few inches could make a big difference in the perceived size of an object.
Don't stress about the quality of your digital camera, it's easy to find yourself going nuts when it comes to photographic equipment, any camera is capable of producing a perfect picture. Yes, there is some cameras that will give you a wider dynamic range and more responsive AF system but the photo comes down to composition.
Wait for the right lighting, thinking about the light terms of it's quality, quantity,and direction.
Shoot when the light is soft and diffused
Outdoor portraits are better when the shot is under bright light. There is a reason why landscapers photographers set their alarms for early hours.
Bitemark- When an animal or person bites down catching skin and tissue between the upper and lower jaw.
Bitemarks can be preserved through photographs and other documentation, Saliva may be depositied on the skin, making it possible to obtain DnA.
Swabbing the area of the injury is important after you have completed taking photographs and documenting the bite marks.
those made on a living victim are less distinctive than those inflicted on a victim after the heart has quit pumping blood.
Antemortem bites- Thoose made on a living victim are less distinctive than those inflicted on a victim after the heart has quit pumping blood.
Postmortem bitemarks-Have well-defined indentions but no bruising because the blood was circulating when the injury occurred.
When collecting Antemortem & Postmortem bites
Swab the area immediately ( to be able to retrieve any DNA that might have been transferred to the victim from the assailant)
Do not swab over impression
Attend to areas behind the teeth
a casting medium composed of calcium sulfate (plaster of Paris) with potassium sulfate added for greater hardness.
preferred over plaster of Paris because it is harder and less brittle.
commonly used for casting footwear and and tire impressions.
it is readily available, inexpensive, and easy to transport.
insert a video showing
Impressions in Snow
electrostatic dust print lifter
Three-dimensional footwear impressions should be photographed without a scale then cast, then photographed again with a scale.
Oblique lighting techniques to highlight the ridges and grooves of the impressions from various angles prior to casting the print.
a device that utilizes an electrical charge applied to a metallized lifting mat that will attract positively charged dust particles; this results in a mirror image of impression made by footwear or tires.
Although snow is a perfect medium many complications EXSIST WHILE COLLECTING IT. at any
moment tire track or footwear impressions can melt or be filled with more snow due to snow
being transient. never cover snow impressions with plastic -this could cause them to melt or
degrade, making it impossible to preserve the original evidence. it can be difficult to
photograph because its white, but it also reflects. The impression is usually sprayed by a gray
primer paint to highlight the ridges and grooves, this makes it easier to photograph.
After swabbing the area for DNA...
Place a piece of clear acetate to the examination
Trace the marks using a permanent marker
Involve a odontaligist at the beginning of investigation
Use medical personnel ( recognizes bitemarks)
Examine and evaluate bite marks to a reasonable degree
4 findings that can be related to the examination of bitemarks provided a suspect has been identifeid...
1.) Definite- To the exclusion of all others (i.e,only suspect could have made the bitemark expression)
2.) Consistent- No features present that will exclude the suspect
3.) Possible- Due to nature of injury, unable to positively confirm or exclude the suspect
4.) Exclusionary- Definitely not made by the suspect
- Food may have bitemarks, saliva may be present that can establish a linkage between the victim, the perpetrator and the scene.
should be made by a forensic odontologist or atleast a practicing dentist.
Offensive bitemark- More clearly defined and generally occur as postmortem bites.
Better defined when bitemark comparison
Teeth may leave scrapes or compression marks on the skin
Important when establishing linkages between victims and suspect