APPLYING GEOCHEMICAL ANALYSIS OF MICA GRAINS TO FORENSIC INVESTIGATIONS- A STATUS REPORT: NORTH CAROLINA V. BRADLEY COOPER, WAKE COUNTY, NC

Mica analysis of soil evidence was used for the first time in the North Carolina court system in the first degree murder trail of North Carolina v. Jordan Peterson to determine if a physical link existed between a suspect and a crime scene (Hanna et al., 2011). White mica grains were later examined in association with another first degree murder trial - North Carolina v. Bradley Cooper – to again determine the possibility of a physical link between a defendant and the crime scene. Evidence soil samples were examined from: 1) a pair of running shoes belonging to the defendant, 2) the crime scene (location of the victim’s body), 3) the defendant’s residence and 4) an area the defendant was known to have traversed (Lochmere Lake area). White mica was identified in all samples except for the defendant’s residence.

Individual white mica grains collected from soil evidence were analyzed for major elemental compositions using a JEOL JXA 8530F Hyperprobe at Fayetteville State University in Fayetteville, NC. White mica from the defendant’s shoes and Lochmere Lake area were compared to elemental compositions of mica grains from the crime scene. All analyzed sources showed two populations of mica: one high in magnesium and one low in magnesium. The two populations were plotted on separate diagrams for interpretation. Compositional fields for micas from the shoes are most consistent with micas from the Lochmere Lake area for the high-magnesium group, and consistent with a possible unknown source for the low-magnesium group.

When a visual comparison was conducted, the presence of fine-grained white mica masses was noted in samples from the crime scene and the running shoes, but was not present in material collected from the Lochmere Lake area or from the vicinity of the defendant’s residence. Due to the size and orientation of the individual white mica flakes in the mica masses and instrument capabilities, elemental analyses could not be conducted on the mica masses.

The data indicated a physical link between the defendant and a location he was known to have been, which further supports the validity of using mineral grain compositions in forensic investigations.