Forensic science must operate in a legal context. The ultimate result of many scientific analyzes is in a courtroom and the admissibility of this evidence is controlled by rules of evidence. Forensic science is part of the criminal investigation process which starts with the discovery of a crime. It is crucial that crime scene technicians properly recognize, collect, and preserve evidence as it has to be effectively analyzed by forensic scientists. There are Constitutional and other legal constraints on how a criminal investigation can be carried out. These include discovery, search and seizure, protection against self-incrimination, and due process. The production of evidence at a trial is compelled by a subpoena, and order to appear in court. The admissibility of evidence is controlled by a set of rules that govern the security of the evidence, authenticity, relevance, and other issues. Scientific evidence is subject to all of these constraints as well as some that apply only to this type of evidence.