Glass examinations can provide information such as, the possible type of glass source (vehicle, container, architectural sample). Glass comparisons can determine whether particles of glass could have originated from a broken source of glass. Examinations typically compare the physical properties (color, thickness, and type), refractive index, and elemental composition of the evidentiary sample to known samples. Glass fracture examinations may help determine a sequence of events, by observing direction and the type of breaking force. A physical fit may also be possible when two pieces of glass fracture fit together, which is a way of indicating that they were once part of the same object.
The Sacramento County District Attorney’s Office Laboratory of Forensic Services Trace Evidence Section, uses Laser Induced Breakdown Spectroscopy (LIBS) and/or Laser Ablation-Inductively Couple Plasma-Mass Spectrometry (LA-ICP-MS). In many glass cases, analytical laser techniques are at the forefront of forensic glass comparisons. These laser methods evaluate some of the main elemental components of glass (Ca, Na) and also examine trace elemental components of glass (Li, Ba, Pb, Sr, Zr, etc.). Our lab is one of the few in the nation able to provide LA-ICP-MS capabilities on small fragments of glass (roughly the size of a small watermelon seed). We provide glass analysis services for our law enforcement partners who may not have access to this type of technology.