SCI 114 8/2
IMPRESSION EXPERIMENT
Post Laboratory Questions
To be answered individually and turned in next laboratory class in a typed document.
1. In general, how is impression evidence recorded and collected?
2. Are impressions classified or individualized? Explain.
3. Can dental stone be used to cast an impression found in snow? Why or why not?
4. List three types of items that can also leave impressions.
5. If impressions are left on the skin, what limitations are there to making a match?
Exercise: Unknown Analysis
1. Review the unknown on Blackboard en,tied Impression Unknown.
2. Identify the unknown imprints or impressions and detail any individualistic
characteristics.
3. Compare the unknown to the two sets of Impression databases (one containing letters,
one containing numbers) and report your conclusion
Report Page – Unknown Analysis
Unknown ________ is consistent with ____________________________________
BLOOD EXPERIMENT
Post Laboratory Questions
1. What would it mean if a reagent had turned color directly upon addition to the sample
prior to addition of hydrogen peroxide?
2. Is blood a form of class or individual evidence? Explain your answer.
3. What is a presumptive test? What is a confirmatory test?
4. Why is it a good idea to perform a presumptive test before performing a confirmatory
test?
5. Was any of your evidence definitely identified as blood? Explain your answer.
6. What is the purpose of a positive control and a negative control?
7. What type of packaging should not be used for biological evidence? Why? What type of
packaging should be used instead for articles containing biological evidence?
Exercise: Identification of Unknown
1. Open the Blood Unknown on Blackboard and follow the instructions there.
2. Identify each of the unknowns.
3. Report your results
Report Page – Unknown Analysis
Unknown is _____________________________ with blood
BLOOD SPLATTER EXPERIMENT
1.How does the diameter of a blood spot vary with increasing distance from which it
fell?
2. How does the substrate which the blood droplet has landed, effect the over all blood
pattern?
3.What is the effect of angle of impact on the resulting blood droplet pattern?
WATCH – https://www.youtube.com/watch?v=0jltioeaEyY&t=16s
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