Challenging expert evidence – It is in (y)our DNA

DNA is considered to be one of the most robust forensic sciences. It can serve as convincing evidence of a person's innocence, however, the gold standard attributed to its accuracy can be misleading where DNA evidence is contaminated or otherwise compromised. The inclination towards assuming its accuracy carries with it the risk of miscarriages of justice.

Our genetic code is signified through a sequence of letters and it is the order of these letters which makes us who we are. When this unique sequence is taken from a crime scene and the DNA profile is compared to that of a suspect, it can be compelling evidence of guilt.

However, taken for inculpatory purposes in isolation of other evidence has led to wrongful convictions.¹ In R v Jama (2009), for example, the sole evidence was contaminated DNA evidence, which led barrister Saul Holt QC to warn: