Tuesday, October 18, 2011

A Rape Case In Sweden


by Andrea Campbell

I am never surprised at the results that can be achieved with forensic science. It is comforting to know that as time moves on, so do improvements in evidence collection and evaluation. Today’s story illustrates these ideas and even though it happened in Sweden, we are happy to see a righteous outcome.

High-Intensity UV Lamps
Body fluids are an important part of a crime scene, in murder and especially with sexually-based crimes. Since body fluids have properties that make them fluoresce under alternate light, it makes sense to walk the scene carefully with the light in hand and mark all the stains with cones or markers that may prove to be clues later on. The light won’t tell you what you’re looking at, but after collection and examination, you may get DNA and other readings.

The Rape in Sweden
On a cold day in Sweden, crime scene investigator Birgitta Jansson, who is with the Karlstad, Sweden police technical division, walked through the snow. It was dawn at about 7:20 in the morning and the sun was waiting to rise over the horizon. An outdoor scene, the crime was committed in a residential area near the center of town, and not far from a school. The case was an alleged rape and it took place at the corner of a hockey rink in a snow drift.

The snow left behind some obvious impressions: the shape of a human figure—arms, legs and torso—that were clear enough. In addition to the visual evidence were some Swedish coins that had fallen from the perpetrator’s pockets that were lodged deep in the snow. Blood was also found near the coins, and all were subsequently collected as evidence.

Investigators then used a high-intensity ultraviolet light to illuminate the scene, just as the sun was beginning to rise. Three spots, thought to be semen, were found in a 4 x 4-inch area.

“The light made the semen fluoresce in the snow, to the extent that I never thought possible,” said Jansson. “Actually, I was amazed that it worked. I never thought you could distinguish semen from snow with the help of a high-intensity UV light. And there was no doubt—the fluorescence was incredibly strong and clear. I have never seen anything like it.”

Jansson examined the glowing pieces more closely and found that they were now frozen liquid laying separate from the snow. They secured and collected those lumps of ice and packed them into bio bags, stored them in the freezer in the police car, in the hopes of sending the frozen liquid to the laboratory.

Back at the Laboratory
Once the lab examined the frozen, cube-like evidence it was clear that there were both semen and vaginal secretions. The sperm produced DNA and was ultimately matched to the vaginal swabs taken from the victim. The rapist was subsequently tried, convicted and sentenced.

The Fluids That Fluoresce
Semen, vaginal secretions, urine, sweat and saliva are all bodily fluids that will fluoresce under UV light. Urine is the easiest to detect, followed by semen, and the others will too, only more often very faintly.

Rehn, Lisel, “Semen fluoresced in the snow solved a rape case in Sweden,” Evidence Technology Magazine, July-August 2011, pp 24-25.
DNA photo: US National Library of Medicine 
photo (right): jah~

2 comments:

Cozy in Texas said...

Amazing how "evidence" has changed.
Ann

Sandy said...

How en-'lightening'!! TNX