Deductive reasoning and logic
- 1. Deductive reasoning and logic Making connections
- 2. How crime scene analysis works • The first step to crime scene analysis is making observations. • Observations lead to questions…or…problem statements. • Example: What crime was committed? Who committed this crime? How was this crime committed?
- 3. Using logic Logic: a system of reasoning and inferences (conclusions that are based on observations) • In context of forensics: does the evidence and the description make sense?
- 4. • Example: A body was found in an alley. The body had multiple stab wounds but there is very little blood at the crime scene. • What is one logical explanation/inference of the crime that you can make with this information?
- 5. Deductive reasoning Deductive reasoning: A thought process that investigators use to assemble the pieces of a criminal puzzle to reach a logical conclusion.
- 6. Looking at facts (AN example of deductive reasoning) • Facts: – Ice cream sales go down in the winter – Statistics show that there are fewer instances of domestic violence in the winter • Facts: – Ice cream sales go up in the summer – Statistics show that there are more instances of domestic violence in the summer
- 7. What is the logical link? • When ice cream sales go up domestic violence goes up. • When ice cream sales go down domestic violence goes down. • Conclusion: The more ice cream that is sold, the more domestic violence there will be…the less ice cream sold the less domestic violence
- 8. Cause and effect • Describe the cause and effect of ice cream and domestic violence… • If ice cream sales stop then domestic violence will also stop. • Do the two really go together?
- 9. • While it may seem like the two go together, it does not mean that ice cream sales really effect domestic violence
- 10. • What we see when we look at the facts is a relationship that really doesn’t exist because we are only seeing a part of the whole picture…leading to misinterpretation • What are some other pieces of the puzzle that we haven’t seen yet?
- 11. Reasoning • False reasoning, as we just saw, can lead to errors and misunderstandings or misinterpretation when evaluating evidence and results.
- 12. Sound reasoning • As experts with a lot of experience, many forensic scientists use a combination of suspicion and reasoning to help solve crimes. • Using sound reasoning allows for valuable interpretation of evidence while still maintaining objectivity