Class and Individual Characteristics
All evidence bears class characteristics. Individual characteristics may or may not be present.
Evidence that possesses class characteristics may be referred to as class evidence. Similarly, evidence that possesses individual characteristics may be referred to as individual evidence.
Both class and individual evidence have value; however, it typically takes considerably more class evidence (and time for collection and analysis) to have the same weight and significance as a single item of individual evidence.
Criminal cases based solely on class evidence are more difficult to prove and require more work, but the results can be just as significant. To put it in perspective, in terms of probative value in the courtroom, it usually takes a considerable combination of class evidence to equate to a single item of individual evidence.
|Class and Individual Characteristics
Measurable features of an item that indicate a restricted group source based on design factors determined prior to manufacture
May be shown to be like or consistent with a questioned source, although not uniquely identifiable with that source
- Width of the tip of a screwdriver
- Width of land and groove impressions
Example of lands
Discernible surface features of an object, more restrictive than class characteristics
Produced incidental to manufacture
Refer to a smaller group source (a subset of the class to which they belong)
May arise from a source that changes over time
- Marks on an object produced by a grinding wheel or sanding belt.
- Manufacturing marks on a group of Ruger firearms
Manufacturing marks on a
group of Ruger firearms
Greg Scala, FDLE, Orlando, FL
- Blood type
Marks on an object produced by the random imperfections or irregularities on the surfaces of the tools used to manufacture the object
Produced incidental to the manufacturing process and typically seen at microscopic level
Can be produced on an object by use, abuse, and/or corrosion
May be uniquely identifiable with a source
- Striated and/or impressed marks produced by the action of the tip of a screwdriver on an object
- Striation marks on a fired bullet
Striation marks on a fired bullet
- DNA profile from a bloodstain