As with all evidence, the investigator or crime scene technician must be concerned with various legal and scientific aspects of collection and preservation of materials. Legally, issues of chain of custody and the necessity ofa search warrant or court order must always be considered. Generally, case law has dictated what is necessary to fulfill the requirements of a chain of custody, as well as for warrants. When in doubt, the investigator should contact the local district attorney's or attorney general's office for guidance.