There are several different ways evidence is collected after a sexual assault. If the assault was recent, within the past 72 hours, you may be directed to seek medical attention so that a medical exam known as a rape kit can be conducted. A rape kit can help collect any DNA evidence belonging to your perpetrator.
Witness statements from individuals who might have witnessed the assault may also be collected. Additional evidence, including surveillance camera footage and other digital evidence, can be used against your perpetrator as well.