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.