ABSTRACT:     Due to advancements in DNA technology, scientists are now able to obtain profiles from samples with lower amounts of DNA than ever before. This increase in sensitivity has led to a higher volume of samples that are being submitted to forensic laboratories with requests to process the samples for “touch” DNA. “Touch” DNA refers to samples where biological fluids are not detected, but there are skin cells that may be left behind due to contact with an item. Often, it is difficult for a sufficient amount of DNA to be collected in order to generate a profile. One of the most common and accepted collection methods in the forensic community has been to vigorously swab an item with a cotton swab and to forward the swab for DNA analysis. In 2014, the M-Vac® system was validated at DNA Labs International (DLI) in an attempt to improve recovery from “touch” DNA samples.

The M-Vac® utilizes similar principles to a wet vacuum. First, using the M-Vac® ’s sampling head, a sterile buffer is sprayed onto the surface of the item. The buffer is then re-collected by applying a vacuum pressure over the sprayed area of the item. The re-collected buffer now contains suspended particles including the DNA that was previously present on the item. The buffer is then poured through a sterile filter under vacuum pressure where the biological material binds to the filter and becomes concentrated. After allowing the filter to dry, the filter can then be sampled and extracted.
Since the M-Vac® was brought online at DLI, it has been used to process a wide variety of sample types including clothing, ropes, cars, bed sheets, and comforters. One of the most common problems that forensic scientists encounter are intimate or indigenous items that belong to an individual in which there is often a great amount of DNA from the owner, but very little from other individuals that came into contact with the item. Furthermore, items with large surface areas or where it is unknown where the perpetrator touched the item are case circumstances where the M-Vac® thrives. Overall, the M-Vac® collection system is a very useful tool for screening evidence. Several notable cases where the M-Vac® was used to improve DNA recovery will be discussed.


Originally submitted and presented at the ISHI Conference, 2015 by Cristina L. Rentas, MFS, Alicia M. Cadenas, MSFS, Rachel H. Oefelein, MSc, and William Hausman, MS, DNA Labs International

Murder of Teen Found Gagged in Bathtub Solved 40 Years Later with M-Vac DNA Collection

 (Photo: Courtesy of the Salt Lake City Police Department)


Sharon Schollmeyers, 16, was found dead in a partially-filled bathtub in her Salt Lake City apartment on Dec. 5, 1977. She had a scarf wrapped around her head as a blindfold and a halter top knotted and stuffed as a gag into her mouth. She was found by her mother, who had come to check on her after the teen had been missing from work that day.

The mother had been let into the apartment by the building manager, who was also the person to call 911 once the body was discovered. The cause of death was strangulation and suffocation, and manner was homicide, investigators determined. But the case went cold, and no one was arrested for her death for four decades.

The employment of a DNA collection method on the 40-year-old evidence at the crime scene has now found, and convicted, the killer.

The killer was the very building manager who let the mother inside the apartment: Patrick McCabe, now 59, authorities said.

The M-Vac System, a wet vacuum DNA collection method, pulled McCabe’s DNA off the halter top gag, decades after police carefully preserved it as evidence, according to authorities. It was the break that finally allowed them to catch up with the long-free killer.

“We are always looking for that piece of the puzzle that will make the difference,” said Greg Wilking, a detective and spokesman of the Salt Lake City Police Department. “In the Sharon Schollmeyers case, the M-Vac came through for us and produced a full DNA profile that we didn’t have before, which led to the CODIS hit.”

McCabe was arrested and charged in Florida earlier this year with the Utah homicide, and has since been convicted of second-degree murder and aggravated burglary. He could face life in prison for the crimes.

Court documents charge McCabe used his building manager’s key to get into the apartment late at night, picked up a butcher knife inside and attacked the sleeping Schollmeyers. He threatened her with the knife as tied her up and raped her, according to the filings.

Schollmeyers’ body was found in six inches of water, complicating some evidence collection. The halter top was submitted for DNA collection in 2013 to the private Sorenson Forensics crime lab right in Salt Lake City. The profile was uploaded to CODIS last year, and a search hit on McCabe in December.

McCabe’s arrest was announced in March by the Salt Lake County District Attorney’s Office. He originally faced a first-degree murder charge which would have been eligible for the death penalty, but McCabe later admitted to the killing. (Local newspapers reported McCabe had previously served time in prison for a sexual offense against a minor in Florida.)

The M-Vac has been employed in prior high-profile cases featured in Forensic Magazine, several of them in Utah, where the company is headquartered. But they’re not all murder convictions: the tool has also exonerated some suspects after lengthy jail terms. Jared Bradley, the company’s president, said the tool is catching on with many local agencies—especially where traditional DNA collection like swabbing has failed to produce genetic material on important pieces of evidence, like murder weapons.

“Agencies that are using the M-Vac, especially for difficult cases or when the evidence is large, rough or porous like in the Schollmeyers case, are getting really impressive results,” Bradley said in a statement upon the McCabe conviction news.

Originally posted in Forensic Magazine  Thu, 06/29/2017 by Seth AugensteinSenior Science Writer – @SethAugenstein

To see original article click here.

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