DNA helping to solve crime

DNA as evidence is changing the court system for the better, according to expertsin the field in Oshawa.

Tom Balka is a criminal lawyer at the local firm O’Brien, Balka & Elrick. He has tried many criminal cases involving DNA evidence and he says he is “always thinking about DNA.”

When defending his client where there is evidence of fluids being collected, he thinks about how it could help his case or how it can be discredited.  The Centre for Forensic Science (CFS) has the responsibility of taking samples and analyzing them for traces of DNA. This DNA can eliminate a suspect, which can be helpful for both the police as well as the defence.

But DNA does not tell the whole story of what happened and does not place blame on anyone, according to Cecilia Hageman. She is a professor at UOIT and worked for the CFS for 22 years.

“DNA is not a test of guilt or innocence,” says Hageman. She is quick to point out that DNA can only place someone at the scene of a crime.

She says results from a DNA sample can only belong to one person. DNA experts can say with confidence there is a one in a trillion chance of it belonging to someone else.

“There is no scientific test for guilt or innocence,” says Hageman. She says when people think that DNA will solve a case that isn’t true because many factors need to be considered. It is up to the Crown and defence to determine the reasons DNA could be found at the scene.

In the past, before DNA, labs would be able to test for blood types but that was limiting in building a profile of a suspect.  Hair analysis was also used in court but often resulted in wrongful convictions, according to Balka.

Balka points out that although DNA might be found at a scene, there could be a reasonable explanation for it being there. For example, if a son is accused of killing his father and his DNA is found at the scene, then there is a reason for that DNA to be there because they live together.

Balka also looks at the way police collected DNA to ensure there was not improper transfer of DNA from one piece of clothing to another in the process.

According to Balka, police are more aware of the importance of forensic evidence in court cases today so they are careful to collect evidence.

Part of that is collecting enough to send to labs. There needs to be enough blood or fluid to create a DNA profile. This can be an issue with cold cases, according to Balka.

When labs open older case files, the DNA samples are often improperly stored because law enforcement didn’t know the importance it would have in the future.

There are cases of samples being used up in previous tests or lost altogether, says Balka.

Although DNA evidence has evolved to become more helpful in eliminating suspects, it is at the mercy of the CFS backlog. According to Balka, a DNA sample can still take months to return if there is a backlog at the lab itself.

Labs have protocols as to how much sample is sufficient to produce a valid DNA profile, according to Hageman, to make sure they have enough of the sample available for testing in the future.

According to Balka, although DNA does not prove guilt or innocence it can change the way the defence strategizes for court. At times, the defence will claim that the defendant wasn’t at the crime scene. If DNA is found, the defence will change to the defendant being at the scene but not involved in the crime.




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Laura is a second year journalism student at Durham College. She enjoys writing for campus, current affairs, and profile for The Chronicle. She loves to read and watch educational documentaries. Her work can be seen on Riot Radio. She hopes to work for CP24.