Podcast
Questions and Answers
What is the primary focus of the Impression Section examiners?
What is the primary focus of the Impression Section examiners?
- Identifying handwriting in questioned documents
- Comparing known shoes or tires to impressions from crime scenes (correct)
- Comparing known substances to chemical evidence
- Analyzing blood samples for DNA matching
Which type of impression can be analyzed as a three-dimensional impression?
Which type of impression can be analyzed as a three-dimensional impression?
- Impressions on car windows
- Impressions on cardboard
- Impressions on glass surfaces
- Impressions in soil or snow (correct)
What is NOT one of the purposes of examining impression evidence?
What is NOT one of the purposes of examining impression evidence?
- Identifying make, design, and size of footwear or tires
- Determining if there are sufficient design features for comparison
- Identifying the presence of fingerprints (correct)
- Comparing questioned impressions to known objects
What must be considered when making a positive identification between the source and impression?
What must be considered when making a positive identification between the source and impression?
Which conclusion can an examiner potentially reach from analyzing impression evidence?
Which conclusion can an examiner potentially reach from analyzing impression evidence?
Why is quick recovery of impression sources important?
Why is quick recovery of impression sources important?
What type of prints are categorized as two-dimensional impressions?
What type of prints are categorized as two-dimensional impressions?
What elements are evaluated to identify a specific tire or footwear item?
What elements are evaluated to identify a specific tire or footwear item?
What should be done to minimize ambient light when photographing impressions?
What should be done to minimize ambient light when photographing impressions?
What is the purpose of taking photos with different aperture settings?
What is the purpose of taking photos with different aperture settings?
How many feet of circumference should be documented for tire impressions?
How many feet of circumference should be documented for tire impressions?
What should be used to enhance contrast in snow impressions?
What should be used to enhance contrast in snow impressions?
Which flash settings are recommended when photographing impressions?
Which flash settings are recommended when photographing impressions?
What type of camera is recommended for photographing three-dimensional impressions?
What type of camera is recommended for photographing three-dimensional impressions?
What is the preferred image format for capturing evidence photographs?
What is the preferred image format for capturing evidence photographs?
What should be avoided when using primer spray paint on snow impressions?
What should be avoided when using primer spray paint on snow impressions?
Why is it important to ensure the scale is at the same depth as the impression?
Why is it important to ensure the scale is at the same depth as the impression?
Why is it important to photograph impressions at a 1:1 ratio?
Why is it important to photograph impressions at a 1:1 ratio?
What is a common technique to ensure continuity when taking multiple photos of an impression?
What is a common technique to ensure continuity when taking multiple photos of an impression?
What should be included in the examination quality photographs alongside the impression?
What should be included in the examination quality photographs alongside the impression?
How should the camera be positioned when photographing the impression?
How should the camera be positioned when photographing the impression?
What is the recommended positioning of the measuring scale in relation to the impression?
What is the recommended positioning of the measuring scale in relation to the impression?
Why should impression evidence be prioritized for early consideration?
Why should impression evidence be prioritized for early consideration?
What angle is recommended for holding the flash when photographing impressions?
What angle is recommended for holding the flash when photographing impressions?
What type of scale is preferably used for impressions?
What type of scale is preferably used for impressions?
What is recommended to practice before collecting evidence impressions?
What is recommended to practice before collecting evidence impressions?
What should be done with moist or damp impressions when collecting evidence?
What should be done with moist or damp impressions when collecting evidence?
What type of media is preferred for submitting images of impressions?
What type of media is preferred for submitting images of impressions?
How should shoes and tires be packaged for evidence submission?
How should shoes and tires be packaged for evidence submission?
What should you avoid using to package the dust lift on EDPL film?
What should you avoid using to package the dust lift on EDPL film?
Which method is NOT suitable for recovering powder developed impressions?
Which method is NOT suitable for recovering powder developed impressions?
What characteristic of Stat-LiftTM is important for its function?
What characteristic of Stat-LiftTM is important for its function?
What should you do after lifting an impression with tape?
What should you do after lifting an impression with tape?
Which tool is specifically mentioned as effective for lifting dust impressions?
Which tool is specifically mentioned as effective for lifting dust impressions?
What does dental stone do when applied to visible residue impressions?
What does dental stone do when applied to visible residue impressions?
What type of materials can dental stone successfully recover impressions from?
What type of materials can dental stone successfully recover impressions from?
What is the advantage of using wider fingerprint tape for lifting impressions?
What is the advantage of using wider fingerprint tape for lifting impressions?
Study Notes
Impression Evidence
- Impression evidence can include shoe or tire impressions in a variety of mediums.
- Three-dimensional impressions occur in materials like soil, snow, sand, and mud.
- Two-dimensional impressions are found on solid surfaces, such as floors, counters, car hoods, and paper
- Examination aims to determine if there are discernible characteristics for comparison
- Examinations can identify make, design, physical size, wear/manufacturing characteristics, and randomly acquired features
- Comparison of questioned impressions with a known object can determine if the object made the impression.
- Possible conclusions include identification, exclusion, or various levels of association.
Collection Guidelines
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Three-Dimensional Impressions (e.g., in soil)
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Method I - Photographic Documentation
- Use a digital SLR camera with the ability to attach an off-camera flash.
- Take photos in the camera's RAW format and convert to TIFF for laboratory submission.
- Use the highest megapixel camera available to achieve 300PPI resolution at size (1:1).
- Photograph impressions using a tripod and aligning the sensor plane directly over the impression.
- Step 6: Include a scale alongside the impression containing identification information. Bury the ruler to approximately the same depth as the impression.
- Step 7: Use low oblique lighting with the flash held approximately three feet from the impression. Photograph at 10°, 30°, and 45° angles to highlight the impression.
- Step 8: Bracket the series of photos, photographing at various aperture settings, such as f8, f11, and f16.
- Step 9: For tire impressions, ensure the entire circumference is documented with overlapping photos.
- Step 10: Lightly sprinkle black fingerprint powder onto snow impressions for contrast. Use black or gray primer paint for highlight purposes.
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Method II - EDPL Lifting
- Not recommended for moist or damp impressions. Practice lifting techniques prior to evidence collection.
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Method III - Lifts
- Gel Lifters are latex with a bonded adhesive layer suitable for lifting and preserving dust impressions.
- Stat-LiftTM is a statically charged film that’s commercially available for lifting dust impressions.
- Wide fingerprint tape is a viable option for two-dimensional impressions. Dust impressions with fingerprint powder before lifting.
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Method IV - Dental Stone Casting
- Best for visible residue impressions. Dental stone absorbs residue material and cleans the surface.
- Cast in the same manner prescribed for three-dimensional impressions.
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Submission Reminders
- Prioritize evidence by searching for it at the approach, entry/exit ways, path through the scene, escape route, near other impressions, and on floors, walls, doors, and the roof. Protect impressions from contamination.
- Practice new techniques on test impressions before working with evidence.
- Use the correct method based on the type and condition of the impression.
- Submit images on a CD or DVD in TIFF format.
- Package shoes in paper bags and each tire separately.
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Description
Explore the key concepts of impression evidence, including shoe and tire impressions in different materials. Learn about the characteristics examined during forensic analysis and the methods for collecting three-dimensional impressions. This quiz will test your understanding of the identification and comparison process in forensic science.
