Using Logic during investigations

Logic is an essential investigation tool. Investigators use several kinds of logical reasoning to create the EBs for the Matrix, position them, and create the links between them. They also use logical reasoning to test the display scenario for completeness and validity. Investigation Catalyst offers guidance, but the investigator must supply the reasoning required to produce the Matrix and analyze it.

Logic for creating a Matrix.

• Tip: follow where the data logically leads you, not your intuition, instincts or experience.
• Tip: sequencing conditions doesn't reveal what happened; sequencing the actions that initiated successive changes in conditions does. Focus on finding those actions.
• Tip: try to make a "mental movie" of what happened in its orderly sequence, to give a structure your investigation.

IF-THEN reasoning is used to

1. Create EBs from observed conditions.

Example: IF you observe this condition or state, THEN you can say that action helped produce the observed state - if you can establish a logical coupled progression.

• Tip: If they survived, and if they haven't told you already, you can ask participants to confirm your reasoning.
• Tip: Objects behave predictably if we know how to "read" what they can tell us. People are less predictable.
• Tip: "Reading" EBs from surviving objects may require expert assistance Don't be hesitant to ask for help.

2. Infer EBs that must have happened if another EB happened

• Tip: A way to do this is to try to make a "mental movie" of the EB and what subsequent actions that may have produced, from what you know thus far. In other words, if this EB occurred, then these other EBs would have happened
• Tip: Track the progression of changes to the final EB in the scenario.
• Tip: suggest, indicate or demonstrate reflect the degree of certainty of the EB. Suggest implies a tentative link, indicate implies a relatively strong link, and demonstrate implies a proven link. Work toward the demonstrate link.

SEQUENTIAL reasoning is used to order Event Blocks (EBs) in their proper time sequence relative to each other. Use sequential reasoning to determine if one EB occurred before or after another EB, based on their timing and spatial relationship.

Example:EB1= the car left the roadway; EB2=the car stopped; and EB3=the car struck a tree

Which had to occur first?

• Tip: use your "mental movie" of the actors in your EBs, and try to "picture" the order in which they acted as the "movie" progresses.
• Tip: use fixed times when you know them, and estimate time before and after those times when you lack complete hard time data.

WHY-BECAUSEor hypothetical reasoning is used to fill gaps in a matrix or to pursue the thread of actions leading backward in time from a know EB, or to hypothesize actions that might have produced a known EB.

• Tip: Use the "mental movie" technique to try to visualize who might have acted during the time of the EBs on both sides of a gap, using your knowledge of the system or people involved or someone else's knowledge, or just guess. Enter tentative EBs containing your ideas and then try to find data that could show the actions occurred.
• Tip: use the general models provided in the Models section to help you frame the answers to your Why questions.
• To pursue the actions backward from a known EB, keep asking why each successive EB occurred, focusing on the people and objects led to the EB, until the origin of the scenario is identified. Trying to "picture" what they or might have done to influence the next EB.

Logic for testing a Matrix.

NECESSARY AND SUFFICIENT reasoning is used to decide if the Matrix describes and explains the occurrence fully and validly.

Each EB and link on a Matrix is examined with this logic test to determine if each EB coupled to a subsequent or "target" EB includes all and only those necessary to produce the target EB every time it occurs. It is a step by step questioning process, that results in establishing the validity of the description and explanation of the occurrence.

Example:

• Tip: start at the end of the matrix and work backwards for most efficient application of this test.
• Tip: this test can be applied as the Matrix is being built to help identify the next investigation tasks
• Remember, sometimes "experts" with knowledge of the system or reasoning skills must be brought in to help investigators with this task.

Logic fallacies

Defective reasoning creates problems for investigators, mostly when introduced by others to support unsupportable points or arguments about what happened or to introduce conjecture. The most effective way to guard against these kinds of problems is to insist on the addition of the disputed EBs to the matrix, and demonstrating the logic problems.

A list of Logic Fallacies, with examples, is available for reference at Starline's web site at http://www.starlinesw.com/product/Guides/MESGuide00.html#a5.