Forensic evidence is most often used to: establish the elements of a crime identify a culprit establish associations between offenders, victim, and so on a and b

The answer is: Establish associations between offenders, victim, and so on

The association is created by finding a link that connected every findings on victim's body and the crime scene with potential individual in police database.
Things such as fingerprints, hairs, saliva, and footprints usually could be used as a solid evidence that associate a certain individual with the crime.