It is important to make correct inclusions and exclusions when narrowing the field of investigation with DNA evidence. Accurately excluding some suspects and including others narrows the field of inquiry and helps to focus scarce resources. The authors note that the contribution that DNA evidence can make to an investigation depends on the circumstances of the crime and the condition of the crime scene. Another issue that is relevant when using DNA evidence in criminal investigations is that proper protocols are followed to avoid contamination and the risk of having the evidence ruled inadmissible. The authors also discuss the challenges of presenting DNA evidence at trial, which includes being able to prove that the DNA evidence was properly obtained and securely transported from the crime scene to the lab. Several examples from Australia about DNA evidence and its admissibility in court are presented. Finally, the authors discuss the use of post-conviction DNA reviews, in which DNA evidence may be used to form the basis of appeals. Examples of Australian cases that have used post-conviction DNA to overturn a court's ruling are cited. Also described is the use of review commissions and innocence panels to investigate cases of suspected wrongful convictions. DNA evidence is used for these reviews where it is available. Finally, the authors discuss the costs and benefits of DNA identification, including issues of privacy and expense.