Ch. 2 Preliminary Tests (Exam 1) Flashcards
What are 2 reasons a false positive may occur (HINT: specificity)?
1) Structural analog present
2) Interferences
What are 2 reasons a false negative may occur (HINT: sensitivity)?
1) Low sample concentration
2) Test isn’t sensitive enough
Which of the following is a reason why presumptive tests are needed? (1) Courts need them, (2) They enable appropriate choice of confirmatory test, (3) Can be done in the field for collection purposes.
All of the above
Why are color tests dangerous/destructive?
They chemically alter the sample and render it useless
This preliminary test detects the presence of semen by identifying the enzyme { }, which creates a purple color indicating a positive result.
What is acid phosphatase, or seminal acid phosphotase?
This is a common confirmatory test for semen that establishes the presence of sperm with red and green color.
What is Christmas Tree Staining?
This test is conducted for the presence of semen but the absence of sperm.
What is prostate-specific antigen (PSA)?
This test for saliva is based on the detection of the enzyme amylase, and clear (or the absence of blue) indicates the presence of saliva.
What is the starch-iodine test?
Acetone, chloroform, and dichloromethane are common solvents used to conduct solubility tests for this sample/evidence.
What is paint?
What is the premise of a solubility test?
Different binder compositions show different solubilities
The Le Rosen test is a solubility paint test used to identify { } compounds.
Aromatic
Diphenylamine is concentrated in sulfuric acid to identify these compounds.
What are cellulose nitrates?
