8127/frame/fm

 
Sidebar 10
 
The Seminal Bloodstain — What’s 
the Question?
The key to the case was reconstructing the movements of the assailant as specifically as possible.
The point of entry was obvious; the screen material on the screen door was cut with a knife.
Immediately inside of the point of entry, the phone cord was also cut through to prevent outside
communication. From there, the assailant’s movements were much more difficult to reconstruct.
This much was clear. He had ransacked much of the house, overturning drawers and belongings
in most of the rooms. Debris was strewn everywhere. The victim was found facedown in the upstairs
hallway, nude, with numerous blunt-force blows to the head. Large blood drops were obvious on her
bedspread and on the floor leading to the hallway, indicating that she had been beaten in the bedroom.
Her pantyhose was tied tightly around her neck, a clue to the cause of death.
Detectives collected the bedspread from the bed, surmising that the sexual assault had occurred
there. They also found a semen stain on the carpet of the room, but this was long before DNA and
DNA databases, so they would have to wait for a suspect before they could do any comparisons. The
latent print examiner was able to lift some prints from several places in the house, including an ornate
money bank from one of the ransacked rooms.
The exit point, however, remained a puzzle. Detectives were not clear if the assailant had exited
through the same cut in the screen door, or used another door. On a concrete pad outside one of the
doors they found a piece of facial tissue. Knowing that the victim was nude, and suspecting a sexual
assault at the scene, one detective surmised that the assailant may have wiped his penis with the tissue,
and later discarded it. If this were true, then the egress would be established. Of course, this door
faced an alley, and the tissue could also easily have been dropped by one of the occupants of the house,
or could simply have been random detritus from the alley.
A primary source of bias in any analysis stems from the person asking the question. This bias
is not, as is commonly thought, geared toward implicating any one person, but rather in too narrowly
circumscribing the possible outcomes of the examination. That is the reason detectives should provide
the crime scene circumstances and the question they are trying to resolve, rather than ask for specific
analyses. In this case, detectives submitted the facial tissue with the request to examine it for semen.
The analyst examined the tissue for semen and, detecting none, dutifully wrote a report saying that
“semen was not detected.”
There the case stood for several years, with no suspect in view. While routinely running unsolved
cases through the fingerprint database, a hit was obtained from a latent lifted from the money bank.
Detectives determined that the suspect was currently in prison for homicide, but that he had been
out at the time of their murder. They went directly to Folsom Prison and arrested him.
As the district attorney was preparing the case, she was puzzled about the facial tissue. She
thought that the door would be a natural exit for the suspect, and suspected that this piece of evidence
might have more to offer. She resubmitted it to the laboratory, this time providing all of the details
of the case. Armed with more information, a different criminalist easily detected a light smear of
blood on the tissue. He performed some blood typing and also determined that the blood showed
genetic types corresponding to those of the victim. With this piece of information, the district attorney
had a more complete case to offer the jury.
While the facial tissue was a small bit of evidence in the overall reconstruction of the crime, the
detective’s preconceived idea that rapists wipe their penises following a rape unnecessarily narrowed
the scope of the examination by the initial criminalist. The more criminalists know about the case, the
greater assistance they can provide in the form of intelligent analyses addressing relevant legal questions.
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Principles and Practice of Criminalistics
detective’s lead and tested the tissue for semen. Only after studying the case
circumstances and determining that the crime was a violent sexual assault,
did the independent analyst think to test for blood. Information about the
case can only assist in choosing appropriate samples to analyze and infor-
mative tests with which to analyze them. Education, training, and experience
provide the analyst with the tools to make good choices.