"Sexual assault kits (SAKs, also referred to as 'rape kits') are used by medical professionals to collect evidence during a forensic medical exam of a sexual assault victim in order to establish elements of a crime. Generally, upon completion of the medical exam the kit is transferred to an authorized law enforcement agency that logs the kit into evidence. Procedure and protocol regarding when and where kits are sent, however, vary across jurisdictions. Some law enforcement agencies automatically send the kits to forensic laboratories for testing while others wait for varying amounts of time; in some cases depending on when/if a police officer or prosecutor requests forensic analysis of the kits. Evidence from these kits may help identify, convict, or exonerate an offender. Evidence may also be stored in DNA [deoxi-ribose nucleic acid] databases for use in other cases. […] The backlog of SAKs has raised concerns over justice for assault victims and that evidence in untested kits could be used to prevent suspects from victimizing others. SAKs may remain untested for reasons such as limited resources of laboratories and law enforcement and police discretion. Police may opt not to pursue a forensic investigation for a variety of reasons including perception of victim cooperation or a decision that the results of the kit would not be pertinent to the overall investigation."
CRS Report for Congress, R44237
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html