What are the characteristics/traits of a good forensic DNA scientist?
The Scientific Method • A procedure used to solve problems or answer questions. • A way of thinking and looking at the world. • A technique used to gather information and reach conclusions.
Steps to the Scientific Method Hypothesis Experiment Conclusion Observation Then revise the hypothesis If the results do not support hypothesis
Principles of Crime Scene Investigation ______ Document the scene ______ Protect the scene ______ Help the victim ______ Search the scene ______ Photograph and draw location of items of evidence ______ Transport evidence to the laboratory ______ Package evidence
Principles of Crime Scene Investigation • Help the victim • Protect the scene • Document the scene • Search the scene • Photograph and draw location of items of evidence • Package evidence • Transport evidence to the laboratory
Search the Scene • Goal- “no stone is left unturned.” • Patterns and search strategies • Squares and rectangles • Concentric circles • Pie configuration
Presumptive vs. Confirmatory Tests • Presumptive • Sensitive • Not specific =many false positives • Confirmatory • Less sensitive • Specific =few to rare false positives
Blood • Presumptive • Luminol • Phenolphthalin • Hemastix • Confirmatory • Takayama crystal test • ABAcard Hematrace
Diffusion • Diffusion- the spontaneous tendency of a substance (solute or solvent) to move from a more concentrated to a less concentrated area. • T or F. Diffusion results in the uniform distribution of a substance.
Spermatozoa • Presumptive • Ultraviolet light • Brentamine reaction • Confirmatory • Christmas tree stain • PSA or P30 • Microscopy
Male Reproductive System Prostatic urethra Spongy urethra Membranous urethra
Saliva • Presumptive • Lugol’s reaction • Confirmatory • Phadebas
Phadebas ® Test Positive test Negative test
Fecal Material • Presumptive • Microscopy for undigested materials • Edelman’s Reagent UV • Apple-green fluorescence
Urine • Presumptive • UV Light • Urea • Litmus paper • Creatinine • Jaffe Test