Case Study: Collected Toilet Paper Provides Key Evidence
This real case exemplifies how an unusual specimen, a piece of toilet paper, affirmed the verdict in a vicious 20-year-old rape case.
It was the early morning hours of a late-winter day in central Pennsylvania. While walking home from a convenience store a woman noticed a man holding a shovel apparently following her. The woman quickened her pace, but the man caught up to her and attacked her with the shovel. He then dragged her between two houses and began to rape her. The man next dragged the victim into a pickup truck and continued the assault. Eventually the victim was able to escape and ran home where she and her husband called the police to report the incident. She was taken to the hospital and treated for injuries to her face (including broken and missing teeth), groin, and genital regions. A sexual assault kit and the clothing the victim wore at the time of the assault, including her jeans, were collected as evidence.
The victim’s description of her assailant caused police to focus on a man who had been seen at another store nearby as police officers patrolled the area around the time of the attack. The victim identified the suspect as her assailant from the second store’s video security tape and from a police photo line-up and he was arrested. Phone records from a pay phone at the second store also placed the suspect in the area.
Prior to examination of the physical evidence, the victim stated her last consensual sexual encounter was with her husband nearly a week before the assault. The victim admitted a sexual affair with a man who worked at the convenience store, but no information regarding their last sexual encounter was provided. The victim’s clothing and her rape kit were tested in 1999 by the Pennsylvania State Police Laboratory. The DNA testing at the police lab found semen from the victim’s husband and at least one other man in a stain on the inside crotch surface of the victim’s jeans. Both the defendant and boyfriend were eliminated as possible contributors. The victim’s rape kit was also examined, but the results of that examination are unknown and no testimony regarding rape kit specimens was given. Since no information regarding a potential second victim paramour was provided, it was argued the second semen source – not the defendant – was the assailant. Despite the absence of incriminating biological/DNA evidence and in the face of potentially exculpatory semen from an unknown source, the defendant was nevertheless convicted of the assault in April 2000.
Over the years of his incarceration, the convicted defendant continued to claim innocence. In April 2017, the victim’s clothing was sent to Forensic Analytical Crime Lab (FACL) to be re-examined as part of a post-conviction investigation. FACL re-sampled the stain in the inside crotch of the jeans to develop DNA profiles for the semen sources using current state-of-the-art DNA technology. As before, a mixture of semen including the victim’s husband was recovered. A unique DNA profile for the second semen source was also determined. The convicted defendant and boyfriend were again both eliminated as this second semen source. The DNA profile for the unknown semen source was submitted to the national Combined DNA Index System (CODIS) database of offender profiles, but there was no hit.
In January 2018, the victim’s rape kit was found and submitted to FACL for examination. We determined semen on the victim’s vaginal swabs originated only from her husband. This finding indicates the semen from the second contributor in the crotch of the victim’s jeans is not likely relevant to the assault.
Also present in the victim’s rape kit was an unusual specimen, a crumpled piece of toilet paper, collected at the hospital when the victim used the restroom. This specimen had been visually examined in 1999 but appeared to be untested. We don’t often see this type of evidence as it is not often collected. In this case, special props are due the nurse who performed the post-assault examination and had the foresight to make sure this seemingly inconsequential specimen was retained.
Stains on the toilet paper were analyzed for male biology at FACL. No semen was detected from the samples however we were able to recover male DNA. Since the male DNA was commingled in an excess of female DNA from the victim, male specific Y-chromosome DNA testing was necessary to help identify the source. Although the result from the Y-chromosome DNA testing revealed a mixture from at least two males, a highly discriminating major Y STR profile was deduced. The convicted defendant could not be eliminated as the major male DNA contributor – proving the convicted defendant’s innocence claim was false.
This real case exemplifies how the investigation of an unusual evidence specimen, a piece of toilet paper, not investigated prior to trial revealed the truth and affirmed the prosecution and verdict in a vicious 20-year-old rape case with an unknown semen source. This complex case also exemplifies the unbiased and comprehensive investigative approach taken by all scientists at FACL. Today’s advanced technologies enable the investigation of more cases, more specimens, and with DNA evidence more minute amounts of biology.
Whether working for the prosecution or the defense, Forensic Analytical Crime Lab prides itself in offering over forty years of continuous experience incorporating cutting edge skills and technology as they become available – a key tenet in our philosophy of applying science to reveal truth.