How are rape kits processed?

Oregon State Police analysts are working to resolve the growing backlog of rape kits, which has quadrupled since the state shipped kits to a private Utah laboratory in 2016.

It takes between 8 and 16 hours to analyze a sexual assault forensic evidence kit, or SAFE kit, and each kit passes through the hands of forensic scientists who specialize in biology and DNA analysis.

The lengthy testing period paired with a limited number of scientists who juggle other casework may have contributed to the growing backlog.

At the Oregon State Police Forensics Services Division at the Portland Metropolitan Forensic Laboratory in Clackamas, each SAFE kit is passed through several analysts, including biologists who analyze hairs and fibers, and scientists who analyze human DNA like saliva, semen and any other swabs taken from a victim.

Forensic scientists first pick up kits from a secure evidence locker after being dropped off by law enforcement agencies and review case notes from the victim, investigating agency and/or sexual assault nurse examiner.

Scientists cuts samples from swabs collected during sexual assault exams including oral swabs, vaginal and cervical swabs, external body swabs, hair samples and pubic hair combings. Kits can range from having four samples up to 20 samples, depending on the type of case.

"We're looking for the type of contact that is described by the patient reporting the assault," said Jessica Buttler, a forensic scientist in the biology processing section of OSP's Forensic Services Division. "We select samples based on that case scenario depicted through the victim's narrative."

In most cases, Buttler said, it can take between an hour and a half to two hours to cut samples from swabs, place them into tubes and search for seminal fluid on clothing or blankets with the help of an alternative light source. 

"I sometimes probably over-document just in case I go to court, so I'm prepared," Buttler said. "We document all physical characteristics like make, model and size of underwear, for example, with the help of a scale for size."

With items like undergarments, Buttler said, scientists focus on the crotch area, where they're looking for vaginal drainage that may harbor semen mixed in from a sexual assault.

Analysts use an alternate light source that shows body fluids fluorescing.

Buttler said it's important to remember that many body fluids pop out under the same wavelength of light, like vaginal drainage, mucous and saliva. This screening process is merely used as an indicator that semen may be present, but it is not definitive.

When the alternate light source demonstrates there may be seminal fluid, Buttler then may conduct presumptive tests, which determines the possibility of the fluid being semen.

Analysts screen for acid phosphatase, an enzyme found in seminal fluid, by comparing an evidence swab sample to a piece of cloth saturated in semen. If the swab turns a purple-pink color within two minutes, it is considered to be a positive result for semen. If it takes longer, the swab is determined to be inconclusive. If the sample doesn't change color, it is a negative result.

After cutting small samples from the swabs and testing for seminal fluid, scientists return swabs into plastic tubing, itemize each piece of evidence with findings and the dates of testing, and seal them in plastic sleeves before handing them over to DNA analysts.

"We're essentially pre-DNA, so we're just selecting samples, taking cuttings and putting them back in the tubes," Buttler said.

The y-screening process

After biology analysts itemize and seal evidence, DNA analysts work to separate male DNA from any other type of DNA found in a sample.

In May 2016, OSP started using a process referred to as Y-screening on kits. Before that, kits were screened for the presence of any biological material. The entire process took between 8 and 16 hours for each kit.

Now with y-screening, analysts are able to find the presence of just male DNA as opposed to any biological material. The new method shaved hours from analyzing time and can take between 6.5 hours to 2.5 hours to process, depending on if male DNA is uncovered. .

Heather Feaman, a forensic scientist with OSP's Forensics Services Division, breaks down the DNA samples with the use of what she calls robots, machines that shake samples in tubes and subsequently separates seminal fluid from any other type of DNA.

"The DNA is magnetized and basically sticks to a magnet just outside of the tube, and will remain while all other DNA is rinsed out from the robot," Feaman said. "The robots are pretty slick."

After purifying the DNA, analysts modify the DNA by determining what kind of DNA is present. If there is DNA present, Feaman said, she specifically looks for y-chromosomes.

While the new process shaves time off of the hours-long analysis, Feaman said, it is only helpful when the suspect is already known.

If the suspect isn't known to the victim, the perpetrator's DNA profile is compared to other profiles. An additional drawback lies in the y-chromosome itself, as it is identical in families with a father, son, uncle or grandfather. That y-chromosome is shared with all male members of the family and can't be differentiated from each other.

"A DNA profile couldn't distinguish between a parent from a son because the father shares his entire y-chromosome to his son," Feaman said. "There are rarely genetic mutations where the DNA would be different."

In the final step of DNA analysis, Feaman separates the suspect's DNA profile by using capillary electrophoresis, which moves DNA through evidence tubes at different rates of speed depending on their negative or positive charge through an electric field. A laser inside the machine tags a piece of DNA as it fluoresces, which indicates male DNA.

That information is translated into raw data by the machine, where scientists can analyze a series of bar graphs indicating different types of DNA uncovered from the testing.

"This is the DNA profile," Feaman said, pointing at the different bars that indicate the victim from the suspect. "The higher the peak the more DNA is in that sample."

If the testing demonstrates a strong profile of the suspected perpetrator, a profile is created from the kit and dropped into CODIS, or Combined DNA Index System, which is a national database that contains DNA profiles compiled by local, state and federal participating agencies according to the FBI.

The forensic profile developed by a processed SAFE kit is searched against CODIS to determine if the profile matches profiles of convicted offenders or those who have been arrested by agencies who utilize the database.

"We've definitely fine-tuned our procedure in the last year but I think it will take some time to get through the backlog," Feaman said. "Once we do, it will be a very smooth system."

The original SAFE kit along with its contents returns to the investigating agency for their records, and in the event the case goes to court and additional testing is required. All evidence is itemized and documented in OSP's evidence database.

While OSP notifies CODIS of a prospective profile match, it is the investigating agency's role to pursue an investigation and arrest of a suspect.

Laboratories that analyze SAFE kits are not notified if their analysis leads to an arrest or conviction of a suspect. Participating laboratories are not required to track local or state conviction rates based on the analysis conducted by its scientists, according to the FBI.

The drawback of this system? There can be a profile in the database detailing a suspect's DNA profile but still lack a name, in the event the suspect has not been arrested or convicted of a crime.

"Maybe we identify the DNA profile, but that doesn’t mean we can identify who they are," Fugate said. "If they've never committed a crime or been arrested, we don't know."

© 2017 KGW-TV


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