Evidence analysis is a process in which evidence related to a criminal trial is analyzed to learn more about it. While some evidence may provide all the information one might need with a surface examination, often, the evidence needs to be explored more deeply. This process is conducted by a technician who specializes in the techniques used to analyze evidence, and has been trained in the proper care and handling of evidence, to ensure that evidence is not compromised during the analysis process.
In the field, investigators collect anything and everything which might be relevant to a crime, assuming that it would be better to have too much information than too little. Before being collected, every piece of evidence is photographed in situ to give the technician and investigators a frame of reference. Then, the evidence is collected in a container appropriate to the evidence type, before being labeled and tagged. The label includes data about who collected the evidence, where it was found, and when it was collected. Then, it can be taken to the lab for processing and evidence analysis.
During the evidence analysis process, cameras are often used to document every step of the process. This can prove useful in court when techniques are challenged or the lab is accused of mishandling the evidence. It also ensures that if evidence is damaged or destroyed, a record of the evidence and the analysis process still exists. The technician first examines the evidence visually to determine which sort of processes might be appropriate for analyzing it, and to formulate a description, such as “swatch of red fabric” or “reference sample from nanny,” which will be used to open a file containing information about the evidence and the processes used to investigate it.
For example, if a glass with some liquid in it is entered into evidence, the technician might want to see if fingerprints can be removed from the glass, and the contents of the glass would be analyzed to determine what was inside. The technician might also collect information about the glass which could be used to find out where it was from. Or, biological evidence such as hair or skin might be analyzed for DNA, while mystery substances on the scene might be run through equipment designed to separate out component chemical parts to figure out what those substances are and where they came from.
In some cases, evidence analysis is carried out at a remote lab which specializes in the type of evidence being examined. For example, a police department with limited lab capacity might send textiles out to a lab which processes textiles. The lab can identify the material and gather as much information about it as possible before sending it back to the lead investigator. In other instances, a full service on site lab may handle all of the evidence from a given case.