By NICO SCAVELLA
Tribune Staff Reporter
AN AMERICAN forensic analyst yesterday testified how DNA samples from the man accused of murdering pregnant teacher Marisha Bowen matched the DNA samples obtained from a vaginal swab of the Guyanese woman.
Rachel Oefelein, a forensic DNA analyst at DNA Labs International in Florida, testified before Justice Carolita Bethel about how the DNA profile obtained from a “sperm fraction” found on Bowen’s vaginal swab matched the DNA profile obtained from Allister Williams.
Ms Oefelein said the chance that an unrelated person, chosen at random from the general population, would match that DNA profile is approximately one in every 160 quadrillion individuals.
Additionally, Ms Oefelein said her forensic analysis of Bowen’s fingernail clippings, which showed indications of blood matter, revealed a DNA profile “foreign” to the victim.
And that foreign DNA profile, Ms Oefelein said, indicated at least one male contributor. Ms Oefelein said Williams could not be ruled out as a possible contributor to that foreign DNA profile, thus, it was reanalysed using probabilistic genotyping methods.
Due to it being reanalysed, Ms Oefelein said the DNA profile obtained from the fingernail clippings is approximately 31,000 times more probable if the sample originated from Williams and Bowen than if it originated from Bowen and an unknown person.
Therefore, she said there is very strong support that Williams and Bowen contributed to that mixed DNA profile, rather than Bowen and an unknown person.
The aforementioned information is contained in two reports prepared by Ms Oefelein, one dated January 12, 2017 and one dated April 24, 2018. The former report contains the analyses of other specimens that were turned over to DNA Labs Intl for analysis, such as bed sheet cuttings, locus swabs, oral swabs, and belt buckle swabs.
Williams is on trial over allegations he murdered the former CW Saunders Baptist teacher on September 9, 2016.
He is charged with murder, robbery, and receiving in connection with the incident. Concerning the robbery charge, it is alleged Williams also robbed Bowen of two cell phones and an iPod.
According to initial reports, Bowen, who was pregnant, was found shortly after 8am on the date in question by other tenants of a complex on Red Sea Road, off Sumner Street, suffering from a single wound to the body.
She was pronounced dead at the scene.
During previous proceedings, Detective Corporal Javod Frazer said how he saw blood on walls, the floor and miscellaneous items in the Guyanese woman’s apartment before ultimately finding her “lifeless” and “nude” body lying in a “large accumulation” of blood in her bed.
Det Cpl Frazer said the woman had what appeared to be a yellow dress with suspected blood covering her face, as well as a black cloth belt wrapped around her neck. He said he noticed visible injuries to the woman’s neck and chin and also a grey towel with blood stains in the area of her right arm.
Det Cpl Frazer also said while at the Rand Lab at Princess Margaret Hospital just days later, he noted that Ms Bowen had sustained multiple injuries to her neck and chin, both eyelids, the insides of both her upper and lower lips, as well as injuries to the right side of her upper back and rear of her upper right arm.
After the autopsy commenced in his presence, Det Cpl Frazer said Dr Caryn Sands, the pathologist conducting the operation, further pointed out injuries to the left and right sides of Ms Bowen’s skull, and also pointed out an embryo.
The trial continues.