An RCMP expert testifying at Ibrahim Ali's murder trial told the court she has never seen a DNA match as close as the one between the suspect and samples found on his alleged victim — except for DNA matches between identical twins.
Forensic biologist Christine Crossman said police investigators were very thorough in their collection and testing of genetic samples from the body of the 13-year-old girl, whose identity is protected by a publication ban.
Crossman told the court only the DNA of Ali and the girl was detected from swabs of the girl's vaginal area, where sperm cells yielded samples that matched Ali’s DNA.
Ali has pleaded not guilty to first-degree murder in the killing of the girl whose body was found in a Burnaby, B.C., park six years ago.
"In any type of occurrence in which there is possibly a sexual component, the best exhibits from a biology perspective are internal swabs from the alleged complainant or victim," Crossman said about how the forensic lab prioritized testing of the girl's swabs.
She said the lab also received other material, including swabs or samples from the victim's neck, nipples, fingernails, hair and clothing.
Only some of these were tested and did not turn up identifiable DNA from anyone other than the girl herself.
"There was no need to examine further exhibits unless the scenario (about what occurred) changed," Crossman told the court.
Crossman told the B.C. Supreme Court on Wednesday that police obtained a "cast-off" DNA sample from Ali in the form of a discarded cigarette butt in August 2018, matching it to an unknown male's genetic material found on the girl's body.
The match led to the police getting a warrant to formally obtain a sample from Ali, which again matched DNA from the body that was found in Burnaby's Central Park.
The defence has not yet revealed its theory of events to the jury.
Crown prosecutors said earlier that the court would hear evidence that showed the murder was random but that Ali sexually assaulted the girl.
A pathologist who conducted the autopsy on the girl testified earlier that she died by strangulation, and a medical examination found injuries such as bruising, scraping and tearing on the back of her head, as well as to her face, arms and legs.
