what are the characteristics/traits of a good forensic dna scientist?

• 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

Observation Hypothesis Experiment Conclusion

If the results do not support hypothesis

Then revise the 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

1. Help the victim

2. Protect the scene

3. Document the scene

4. Search the scene

5. Photograph and draw location of items of evidence

6. Package evidence

7. 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

Luminol

Luminol

Hemastix

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

P30 Analysis- ABAcard

Male Reproductive System

Prostatic urethra

Spongy urethra

Membranousurethra

23

Salivary Glands

Saliva

• Presumptive– Lugol’s reaction

• Confirmatory– Phadebas

Phadebas ® Test

Positive testNegative 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