At the heart of any criminal case is the establishment of the identity of the perpetrator so that he or she may be meted out the punishment commensurate to the crime that has been committed. In cases where there is an eyewitness, a line-up will be conducted, and the witnesses will identify, to the best of their knowledge, the person they saw during that particular time. However, a positive ID does not guarantee a conviction, unless the witness saw the actual crime being committed.
If no witnesses have come forward, then it is up to the forensics team to do a thorough analysis of the crime scene, including the body of the victim. For crime scenes, it is important that police be able to preserve the scene as it was discovered to ensure the patency of any forensic information that will be gathered from it. Again, as part of evidence in a criminal case, care must be taken when conducting investigation because the findings might be dismissed based on a technicality or the inability to follow proper court procedures.