Perpetrators of sexual assault, like any other predator, generally target a victim easy to access and overpower. Targets are often women, children and thoseincapacitated mentally or physically. Victims in circumstances where they are vulnerable to attack, such as prostitutes, are common targets. Therefore, when responding to a sexual assault scene, the way the offender gained access to the victim is important in determining the scope of the crime scene. There also may be primary, secondary or multiple scenes.
The first thing needed to preserve physical evidence is to secure the scene, ensuring the safety of the victim and witnesses. A log of all persons at the scene is important, including emergency personnel. They may be required to submit samples of hair, DNA, etc., at a later date to rule them in or out as a source of the evidence at the scene.
In some cases emergency personnel may have arrived on the scene before the police. They may have noticed a vehicle or person of interest upon arrival. They may also have experienced transient evidence, such as odors, at the scene. Witnesses should be separated and asked for the basic facts as well as any vehicle descriptions or descriptions of people leaving the scene.
Medical personnel can be asked to help preserve evidence in several ways. First, if there are pools of liquid, such as blood on the ground or floor, the stretcher can be carried around the material rather than wheeled. Wheel tracks through liquid or soil can contaminate the material.
Any clothing removed from the victim can be placed in a clean paper evidence bag and sealed.
If the victim has sustained bruises, bite marks, stab wounds, gunshot wounds or tool marks from other weapons, it is important medical personnel avoid inserting chest tubes, needles or IVs through these marks. Of course this may not be possible but preservation of the injury patterns can be important.
Normally, no evidence is removed from a crime scene before being photographed and added to the crime scene sketch. The victim is the only part of the crime scene that is removed from the scene prior to processing, and much of the physical evidence may be on the victim's body. If the victim is being transported to a hospital, efforts can be made to preserve evidence by bagging the hands and hair. Of course if this causes the victim further trauma it should be avoided.
To maintain the chain of custody where evidence on the victim is concerned, whenever possible an officer should accompany the victim to the hospital. If clothing or other items are removed from the victim, the officer can properly bag and label them.
If it is not possible to accompany the victim in an ambulance, then simply giving the ambulance personnel some evidence bags (paper for clothing) and asking them to place the victim's clothing in them may help preserve DNA, hair, fiber, glass, gunshot residue and all sorts of other trace evidence.
The hospital can be advised en route that a sexual assault nurse examiner (S.A.N.E.) is required. These nurses (sometimes doctors) are specially trained in examining sexual assault victims. They also are trained to recognize and preserve unique evidence of sexual assault. These nurses are most often emergency nurses who work as sexual assault examiners on an on-call basis.
The nurses work with the police, medical staff and victim services to preserve evidence with out further traumatizing a victim.
In remote communities there may be no immediate access to specially trained personnel. It is advisable to know the location of the nearest hospital equipped to conduct sexual assault exams and provide counseling if needed.
Once the victim and witnesses have been removed from the scene, and the evaluation of the scope of the scene is done, collection of evidence can proceed.
There is no particular order in which evidence is collected. The investigator in charge can determine the order based on where the scene starts and ends. Evidence in danger of contamination or degradation is usually collected first.
Always wear gloves and change them each time a new piece of evidence is collected. Avoid smoking, spitting, eating, sneezing, coughing, and using the washroom at the scene. DNA is contained in body fluids, even in small amounts, and these activities can contaminate a scene.
Wear a mask if biological material seems to be present. Be careful not to place collection kits on furniture inside the scene. This can cause contamination of the evidence collection materials.