The crime of sexual assault can be one of the most difficult cases to investigate. Sometimes the crime is not reported for days, weeks and even years after the occurrence. By that time any trace evidence such as hair, fiber, DNA and other physical evidence will have been destroyed or contaminated.
Often victims will destroy trace evidence by attempting to bathe or wash clothing. When a victim feels they have some how brought on an attack or are too young to understand the nature of the crime, they may attempt to cover up the crime or pretend it did not happen.
Most cases of sexual assault are reported by women from the ages of 14 to 25, but victims can be male or female, young or old.
Assault upon children is especially hard to investigate. Some children are too young to properly explain what has happened to them while others are afraid to come forward either from embarrassment or intimidation.
What makes reporting even more difficult for young people is the age of consent. In some states the age of consent is as low as 11 years of age while others set it as high as 18.
This means children under the age of consent may not seek medical treatment without a parent or guardian present. Children under the age of consent may report to a school guidance counselor, family friend or member of the clergy if they are old enough to be left alone with any of these people.
As the statistics show, the majority of sexual assaults occurring in the United States and Canada are perpetrated by people the victims knew. This makes the use of trace physical evidence difficult to use, even if the assault is reported immediately following.
The reason for this is fairly straightforward. If the victim is assaulted by someone who had legitimate reasons to be in contact with them, it is very difficult, if not impossible, to determine if the evidence got there during an assault or as the result of cross transfer in the environment. Tool marks from weapons or jewelry, and bite marks could have gotten there because both the victim and the perpetrator had access to the same environment, with the exception of semen inside a victim's body,
In the United States, the definitions of what constitutes sexual assault varies widely from state to state. Some states, such as New York, require penetration to have occurred (however slightly), while other states consider any sexual touching, which is unwanted or unsolicited, an offense. Many states have classes of offenses which generally are based on the level of violence, harm to the victim and/or intimidation of a victim through threats of harm to self or loved ones.
The seriousness of the offense increases when the perpetrator is in a position of trust such as a teacher, guardian or other person of authority.
Some states specify the age of the offender as well. It is paramount an investigator knows exactly what the law defines as an offense. The definition will steer the focus of the physical evidence collection. He must know what he is trying to prove using physical evidence before submitting it to a lab.
It is unfortunate to say but the cases providing the best evidence as far as physical evidence, other than semen samples in or on the victims, are those that involve attacks by strangers, which are reported immediately. Immediate reporting increases the chances of the existence of physical evidence. If the attacker is a stranger there should be little reason for hair, fiber, footprints, fingerprints, etc., from the attacker to be on or near the victim and vice versa.
This is especially true if the attack occurs in the victim's home rather than an area with public access. For example, a hair consistent with the suspect found on the victim creates a statistical probability that it got there by coincidence. If, however, the victim's hair is also found on the suspect's clothing, the probability of coincidental cross transfer becomes astronomical.
Some of the following may seem like common sense but several high-profile cases show that it bears repeating.
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.
Do not allow civilians or family members access to the scene. This may sound obvious, but in the Jon Benet Ramsey case, the family and several friends were allowed to stay in the home for hours. In an attempt to alleviate their restlessness, the lone officer at the scene allowed them to search the house.
The girl's body was found by her father in the basement, which had not been previously searched. In this case potential suspects were allowed to roam freely about the scene. Even if they were not the perpetrators of the crime, they surely contaminated and destroyed evidence.
Forensic evidence: What to look for
Almost anything imaginable can be evidence at the scene of a sexual assault. If something looks out of place, collect it even if its connection to the crime or identification is unknown. The following are some of the more common types of evidence.
Body fluids such as semen, saliva, urine, sweat or mucus contain DNA. As well, these types of biological samples can be used for toxicological and serological testing. These tests can reveal the use of particular drugs (toxicology) or things such as blood type (serology). Common sources of this type of evidence are:
- Sheets and other bedding, as well as fabric off furniture and vehicle upholstery
- Window panes and sills outside the residence
There have been cases where perpetrators watched their victims from outside and left body fluids on windows, etc. Cigarettes may be found in locations where the perpetrator hid outside. These are also a source of DNA. Both saliva and skin cells can be found on cigarettes.
- Garbage cans — may contain tissues and used condoms
- Anything that may have been used as a weapon may have skin cells or blood on it
- Broken windows and other glass fragments may have blood from the perpetrator on it.
Perpetrators can cut themselves while breaking windows or other glass items.
- Partially eaten food or gum
- Swabs from the victim's mouth, anus or vagina
- Clothing from the victim or suspect
Standard toxicological screening of the victim's or suspect's blood, urine or saliva can reveal whether drugs (prescription or street) or alcohol were present. The lab can be asked to test for the presence of chemicals associated with benzodiazepines such as Rohypnol.
Date rape drugs. Rohypnol is one of the more prevalent drugs used in the United States as a date rape drug. Originally it was produced as an anti-depressant and a sleeping pill by Hoffman La Roche Pharmaceuticals for use in Europe but has never been approved for use in the states. It was introduced to the country via Mexico in the 1990s.
The drug Rohypnol was originally produced as a white tablet embossed with the word "Roche." It eventually became known as a "date rape" drug, which was commonly administered to unsuspecting victims by mixing it into an alcoholic drink. The manufacturer changed the color, and it is now a green pill implanted with a blue dye, which is easily detected if mixed into a drink. In the United States, the older white pills are most common.
Rohypnol can be smoked, injected or ingested. The effects usually last between 8 and 12 hours. The important thing in terms of forensic evidence is that Rohypnol has a half-life of 9 to 25 hours. After this period it is not detectable in blood samples. It will be detectable in urine samples within 2 to 5 days if the lab is directed to look for significantly smaller concentrations than is the standard.
The first case of the drug being used as a date rape drug occurred in Florida in 1992. To date, several thousand cases have been reported around the country. This figure is probably just the tip of the iceberg due to the low rate of reporting (less than 5 percent). This drug is usually used in combination with alcohol which can produce memory loss. Victims may feel they don't remember enough about the assault to report it.
Rohypnol is known by many street names. Some of the more common names are "roofies," "ruffies," "R-1 and R-2" (indicated in the dosage), "RTF" and "Mexican valium," but new names appear regularly.
GHB. Gamma-hydroxybutyrate is most commonly known as Ecstasy. It is actually a chemical produced naturally in the cells of all mammals. Originally produced in the 1920s, it has been used as an anesthetic and later by athletes as a steroid. It was also available as a pain killer for horses and cattle up until the 1980s, readily available at livestock supply stores.
The drug is often used at raves. It is added to water or other drinks. The effects make the user seem to display the signs of being drunk.
Forensically the drug is very difficult to detect. The half-life is a mere 20 minutes. It is detectable in blood for about 4 hours after use. In urine it is present for about three days.
There are several street names for GHB such as "aminos," "Georgia," "liquid ex.," "goop," "salty water" and "soap" but "Ecstasy" is the most common.
Fibers are commonly found on bedding, carpets and furniture which may have come into contact with the victim or suspect's clothing. Points of entry and exit such as door jams and window sills can have bits of fiber from clothing caught on them. Trees and bushes along the point of entry and exit may have fibers adhering to them.
Scraping from under the victims fingernails may contain fibers. Buttons, zippers and belt buckles from either the victim's clothing or the suspect's may have cross transferred fibers caught in them.
Weapons can be anything from a bottle or tree branch to a firearm. If the type of injury is apparent it is easier to search for the type of weapon used. Weapons create unique tool marks in the form of injury patterns on a victim. The suspect may have left blood or fingerprints on a weapon. Alternately, vagina secretions or blood from a victim may be on a weapon.
Fragments of glass from broken windows, bottles, etc., can tell an investigator many things. Various types of glass are unique in their properties and density. These variations can be used to determine the source of the glass such as window glass or bottle glass. Glass fragments caught in the suspect's clothing which are associated with the crime scene can help place the suspect at the scene.
Radial and concentric fractures as well as stress fractures can determine the direction of impact as well as the point of impact.
Entomological evidence may be present in the form of head or crab lice. It can also be present as insects or parts of insects caught in the victim's or suspect's hair and clothing.
The presence of head or crab lice can be important in linking a suspect to a victim. Entomological evidence can also indicate a location such as indoors or outdoors, country or city or season because all insect have a particular niche in which they live.
Sexually transmitted disease
The presence of any STD can link a victim to a suspect or vice versa. Only in rare cases is this definitive. Unless the victim has been celibate for years as in the case of someone in a coma, someone institutionalized for mental incapacity or too young to engage in sexual activity it is hard to prove the source of the STD.
Wounds incurred in a sexual assault can be of any nature. It may be the victim or the suspect that is wounded.
Of particular interest in sexual assault cases are the wound patterns a victim may have sustained. The victim may lie about the circumstances he or she is in or be unaware what has happened to them. He or she may present themselves to medical staff or police as a recent victim when in reality the assault has occurred several days prior. Having a trained S.A.N.E. nurse or doctor assess the bruising and wounds to see if the time line fits is advisable.
Whether there is bruising around the vulva or tearing at either the 6 or 12 o'clock position is important. This alone is not indicative of sexual assault, but can be a red flag to investigators.
Restraint marks from bondage such as tape, wire, clothing, etc., also can be red flags for investigators. Bruising on the upper arms and inner thighs of both female and male victims may be present. In victims who have been anally penetrated, while on their stomachs, there may be bruising or lacerations between the naval and pubic line. This is caused by friction between the penetrating object and floor.
Bite marks are fairly common in sexual assault and tend to have patterns according to the sex of the victim. Females tend to be bitten on the neck, shoulder, breast and inner thigh and the buttocks. Men tend to be bitten on the upper back, shoulder and scrotum. Any of these injuries are indicators of a sexual assault when in combination with other evidence.
For any of the physical evidence remember to collect exemplar samples from points not associated with the areas where physical evidence is found. For example take fiber samples from areas of bed sheets not associated with stains. This can rule out accidental contamination or false positive results.
Learning how to accurately and smartly collect evidence in sexual assault cases can be the difference between a win or loss in court.