more likely to produce an arrest than stranger-rape cases without forensic evidence. Stranger cases can take a longer time to identify the perpetrator because without forensic evidence, the case becomes significantly more difficult to prosecute. This is one of the main problems that many victims face when coming forward that they had been raped. Acquaintance rape The vast majority of sexual assaults are non-stranger (or "acquaintance") cases where the victim knows the assailant. While identifying a suspect is not at issue, the kit's forensic evidence can be used to confirm offender identity in acquaintance rape cases. The kits may also be used to determine whether the offender committed other crimes. In many acquaintance sexual assault cases, the accused assailant will defend the accusations as consensual encounters. In such cases, rape kit evidence that documents the victim's injuries, e.g., photographs of bruising, is a useful tool to corroborate allegations of non-consensual sexual contact. In cases where the victim suffers a serious injury, filing charges and reaching convictions is more likely. In other acquaintance cases, the assailant may deny that sexual intercourse occurred at all. In such cases, specimens that show either sperm or specific enzymes that are unique to seminal fluid (enzymes prostatic acid phosphates or acid phosphatase) can be used to prove sexual contact. Serial rape cases Serial rape is defined as an assailant that has raped two or more victims. Serial rape may involve sexual partner violence or non-partner sexual violence, and it may be in the same family, in the same or different regions of a city, or in different cities or states. DNA collected by rape kits can help lead to identifying and arresting a person guilty of serial rape. In both stranger and non-stranger sexual assault cases, DNA testing of rape kit evidence and DNA database hits help identify serial sexual assaults. For example, a 2016 study of 900 previously untested rape kits in Detroit, Michigan found 259 CODIS hits, which included stranger and non-stranger sexual assault DNA profiles. Sixty-nine of the hits were serial sexual assault hits, 15 of which were acquaintance (non-stranger) sexual assault cases. In a study analyzing the status of Brazil's DNA database in 2015, researchers found 223 matches related to 78 serial rapists. At the time, the DNA database contained 650 profiles from one type of analysis of samples collected in rape kits—male autosomal STR profiles—and 420 profiles from a second