Homicide investigations, as with all criminal investigations, have to be conducted with two thoughts constantly in mind. The first involves identification of the guilty party or parties. That, of course, is the purpose of most investigations: identification of the individual(s) responsible for the criminal act. There is a reason for the use of the word "most" in the above sentence, however. Investigating agencies may have great confidence in the identity of the guilty party, but still not feel comfortable making an arrest, which brings us to the second part of the equation: the requirement to amass a body of evidence sufficient to convince a jury beyond a reasonable doubt of the suspect's guilt. And it is here where there may be room for improvement in how the police department in question conducts homicide investigations.
The Constitution of the United States guarantees American citizens certain rights, such as the right to not be subjected to unwarranted searches and seizures of property. Additionally, under the landmark Miranda v. State of Arizona case of 1966, the U.S. Supreme Court ruled that suspects do not have to answer questions posed to them by law enforcement officials, the Court having determined that compulsory interrogations violate the suspect's Fifth Amendment right against self-incrimination. All of this is highly relevant to the question posed by the student. Homicide investigators, as with investigators focused on other types of criminal activity, such as armed robbery, cannot cavalierly carry out their investigation without regard to constitutionally protected rights. Also, investigations must be able to withstand the scrutiny of very skilled defense attorneys practiced at finding weaknesses in the prosecution's case, such as whether physical evidence was properly handled at the crime scene. Even a minor error in the handling of evidence can result in a successful motion by the attorney for the defendant in a trial to have that "tainted" evidence thrown out.
A police commissioner seeking to improve the way in which homicide investigations are conducted would, therefore, coordinate carefully with the prosecuting attorney's office to ensure that law enforcement officials, from patrol officers to detectives, are properly trained in the way to secure crime scenes and handle evidence so that there can be no question as to the constitutionality of the investigation. Police officers are not expected to be experts on the law, but the level of knowledge they require to perform their jobs can come awful close. It is the commissioner's responsibility to ensure that precinct commanders are adequately preparing their subordinates for the rigors of carrying out investigations, especially those involving murder.