The purpose of conducting the crime scene search is for the identification and collection of valuable evidence which will serve as the key to resolution of the crime. An investigation would be useless without any evidence that can be recovered from the crime scene. Hair strands, blood stains, finger print, saliva, shoe and tire impression, tool mark, chemical substance, biohazards, gunshot residues or other instrument used for the crime (e. g. gun, knife, hard objects etc.) are among the valuable evidence that could be collected from the crime scene.
There are basically two types of evidence: the testimonial and the physical evidence. Testimonial evidence is a form of a verbal or written statement gathered from the victim/s, witness/es and suspect/s through questioning while physical evidence are objects with size, shape and dimension obtained from the scene of the crime. Again, the concept of physical evidence is based on the Locard’s Principle of Exchange which states that: every contact leaves a trace.
Proper processing of this evidence could lead to the investigative lead, identification of the suspect, confirmation of the victim’s testimony and clearance of the innocent suspect. As the evidence had been collected and preserved, the investigator will take these evidences to the crime laboratory for forensic analysis. The crime laboratory is where the evidence gathered from a crime scene is analyzed in minute detail. Scientific testimony is the deciding factor in the resolution of many criminal cases (Holden). The crime scene is released only when it is reasonably certain that all of the facts and answers have been obtained.
One of the most important responsibilities of the criminalist is the accurate interpretation of the result findings for the determination of the circumstances at the time a crime is occurred, or possibly to support a statement or testimony made by a witness. Reconstructing the events of a crime is often difficult. Forensic scientists use scientific methods, physical evidence, and deductive and inductive reasoning to gain knowledge of the events that surround the commission of a crime. To reconstruct a crime or crime scene requires an understanding of human behavior and the physical laws and processes involved.
Any findings must be conveyed to the other elements of the criminal justice system by written reports or expert and formal testimony. The criminalist must formulate and present conclusions so that technical details are well understood by the court and the jury (Camenson). Forensic examination is a series of steps: recognition, identification, individualization, and reconstruction. A suspect is identified through the first three steps which will lead to individualization or determination of the source of an item of physical evidence. This individualization is made possible through comparison testing.
Fingerprint evidence is the best example of comparison individualization. Recent advances in automated fingerprint identification system (AFIS), and DNA databases (CODIS) allow a single fingerprint or small bloodstain found at a crime scene would be enough for the identification or more properly termed as, individualization of a suspect. Significant developments in the identification of individuals since the advent of fingerprinting, and the resulting legal reforms enacted in the awakening of DNA testing in particular, make the critical assessment of the use of such technologies and their evidential impacts are essential.
These technologies are forensic pathology, forensic toxicology, forensic odontology, forensic anthropology, forensic taphonomy, forensic entomology, forensic engineering, finger printing, iris identification, facial ‘mapping’, voice recognition, DNA analysis techniques, identification of biological fluids and stains, blood stain characterization (James and Nordby), serologic techniques; microanalysis and examination of trace evidence and the use of cyber technology in forensic science (databases, archiving x-ray spectra, video image processing, animation software and use of networks) (Houck).