1. Science of Crime Scenes
Chapter 6.3
Science of Crime Scenes

2. Science of Crime Scenes
Impression Evidence
Epitomize the one- and two-way sharing of materials between human beings and their environment
Pieces
Dust
Smears
Drops
Diffusions
Stains
Science of Crime Scenes

3. Science of Crime Scenes
Human traces
Science of Crime Scenes

4. Science of Crime Scenes
Human traces
DNA
Fingerprints
Palmprints
Bare footprints
Skin
Science of Crime Scenes

5. Science of Crime Scenes
Human traces
Due to today’s high sensitivity of DNA analysis, only a few skin cells are required for DNA analysis
Shed cells are mainly from the outer layers of the skin
Not all cells with produce sufficient DNA
Science of Crime Scenes

6. Science of Crime Scenes
Human skin secretions
Produced by three types of different glands
Apocrine
Found under armpits, in the genital and anal regions, and the chest area
Apocrine secretions are similar to eccrine ones
Eccrine
The palms, soles, and forehead have a stronger concentration of eccrine glands than the rest of the body.
95% of eccrine secretions are composed of water and electrolytes
Sebaceous
found all over the body but are in higher concentration on the face and the head
Quantification of these products to produce a “standard” profile is impossible
Science of Crime Scenes

7. Science of Crime Scenes
Fingerprints
the impressions of ridges and furrows left on a surface touched by friction ridge skin
fingers, hands, toes, feet
Handprints and footprints are deposits of eccrine secretions
Fingerprints are a combination of eccrine and sebaceous secretions
people generally touch their face or scratch their head
Environmental remnants and contaminants come to rest on our hands, adding to the deposited impression
Ex., blood
Science of Crime Scenes

8. Prints are unique, marks are not
The problem is not about the uniqueness of any fingerprint, but
our ability to decipher a fragmented, potentially low-quality, adulterated fingermark
deposited on an uncontrolled surface
on which development choices were made to visualize the mark
with probable background noise attached
Summed up in one word: Fidelity
Science of Crime Scenes

9. Science of Crime Scenes
Implications for CSI
doubtful that the CSI will be able to decide at the scene which fingerprints will be useful for later development and comparison
a consistent chain of development should be understood and applied to improve and optimize the trace detection
the quality of the print will be assessed during the first step of analysis
ultimate decision of source and the weight of the evidence should be made by the trier of fact
Science of Crime Scenes

10. Science of Crime Scenes
DNA possible
DNA jeopardized
DNA not possible
Science of Crime Scenes

11. Science of Crime Scenes
Traditional powder on superglue print (after 24h)
Superglue performed in fume hood
Science of Crime Scenes

12. Stick or adhesive surface flowchart
Science of Crime Scenes

13. Human skin processing flowchart
Science of Crime Scenes

14. Science of Crime Scenes
Porous Surfaces
Science of Crime Scenes

15. Science of Crime Scenes
Nonporous Surfaces
Science of Crime Scenes

16. Science of Crime Scenes
Object traces
Science of Crime Scenes

17. Science of Crime Scenes
Object traces
With sufficient force, any object having contact with any matter has the potential to leave and/or collect a trace
With adequate detection methods, both transferred and received traces can be revealed and related, at least in theory
Natural
Manufactured
Science of Crime Scenes

18. Science of Crime Scenes
Manufactured objects
markings either on them (as with stamped or engraved identifiers)
Markers in them (as with taggants)
lands and grooves in the barrel of firearms
fibers in textiles
glass compositional differences
tread patterns in shoe soles or tire treads
Science of Crime Scenes

19. Science of Crime Scenes
Manufactured objects
use and “wear and tear” of objects leave traces of their “activity history,” like breaks, scratches, and wear
the first challenge is to distinguish which come from the production process (class characteristics) and which come from the specific-use history of the source
Science of Crime Scenes

20. Science of Crime Scenes
Shoe prints
Sherlock Holmes says to Dr. Watson in A Study in Scarlet (1887): “there is no branch of detective science which is so important and so much neglected as the art of tracing footsteps.”
The forms and designs of the soles can be easily described, allowing classification systems
provide relevant information for crime scene reconstruction and can indicate entry access, pathways, exits, and the number of persons involved
other possible information includes assessment of the gender, size and weight of the perpetrator, and the serial deposition of impressions
Science of Crime Scenes

21. Science of Crime Scenes

22. shoemark on ceramic with black powder
Science of Crime Scenes

23. Science of Crime Scenes
Tire marks
allow crime scene reconstruction
vehicle model identification
narrowing if not suggesting a specific tire
linking cases or crime scenes to each other
Science of Crime Scenes

24. Science of Crime Scenes