‘Strands in a cable’: effective investigator decision-making using forensic identification evidence in volume crime investigations

Figures & data

Table 1. Hypothetical burglary scenario.

SCENARIO The victim has come home to find that her kitchen fly screen has been removed and her window forced open. Her laptop has been stolen from the kitchen table. The victim does not smoke and can smell cigarette smoke in her house. She locates a cigarette butt in the garden at the front of her driveway. The victim further identifies a drop of blood on the kitchen floor. There are no witnesses, no vehicle identification, and no CCTV. A crime scene investigator (CSI) attends and locates fingerprints on the inside of the fly screen frame and on the outside of the kitchen window. The CSI further collects the blood from the kitchen floor and the cigarette butt from the garden.

Outcome A: Scientific analysis of the fingerprints on the fly screen identifies a suspect, but no success with the DNA analysis on the cigarette or blood.

Outcome B: Scientific analysis of the fingerprints does not identify a suspect, but the DNA analysis on the cigarette butt does identify a suspect.

Outcome C: Scientific analysis of the blood drop identifies a suspect, but the fingerprint analysis and DNA analysis of the cigarette butt does not identify a suspect.

Figure 1. Decision-making process applying the human reasoning process in volume crime investigations.