ABSTRACT
Because it is automated and produces results quickly, the PCR-STR process is now the usual method of DNA typing employed in forensic laboratories in the United States. However, because the process means that all DNA examined is amplified, whatever its source, samples can be corrupted. Crime scene investigators must take great care when collecting trace evidence. Laboratories must follow very strict procedures to keep each piece of evidence separate and ensure that the chain of custody is logged from individual to individual. It is also vital that investigators are not contaminated by the samples. Biohazards such as hepatitis and HIV are particularly dangerous, so they must wear gloves at all times, frequently changing and disposing of them safely.
