Activity-Level Interpretation
Definition
An opinion about what activity produced or deposited the evidence, rather than simply what the source of the evidence is. Activity-level conclusions require background data on transfer and persistence and are more uncertain than source-level ones.
- Question addressed
- What activity produced or deposited the evidence
- Contrast
- Source-level, what the source of evidence is
- Requirement
- Background data on transfer and persistence
- Certainty level
- More uncertain than source-level conclusions
Common questions
Why is activity-level interpretation considered more uncertain than source-level interpretation?+
It depends on additional assumptions about how material transfers between surfaces and how long it persists, factors that vary by material type, contact force, and time elapsed, whereas source-level conclusions only need to establish where material came from.
What evidence does an expert need before offering an activity-level opinion?+
Empirical data on transfer and persistence rates for the material and scenario in question, gathered from validation studies or case-specific experiments, rather than intuition about how the deposit might have occurred.
Related terms
- Bayesian Reasoning
- A framework for updating beliefs in the light of evidence. Prior probabilities are combined with the likelihood of the evidence to produce...
- Hierarchy of Propositions
- A framework that classifies forensic questions at source level (where did this come from?), activity level (what was the person doing?), and...
- Hypothesis
- A proposed explanation for observed evidence. In reconstruction, competing hypotheses are evaluated against the physical facts and background knowledge. A good hypothesis...
- Likelihood Ratio (LR)
- The ratio of two conditional probabilities: the probability of the observed evidence given the prosecution's hypothesis (same source), divided by the probability...
- Reconstruction
- The stage at which all analytical findings are assembled into a coherent account of how an event unfolded. Reconstruction draws on scene...