Many people in Minneapolis-St. Paul know how the story goes: a man is arrested and accused of rape. As police, investigators and prosecutors try to build a case of sexual assault against the suspect, forensic experts discover some evidence that conclusively ties the suspect to the crime, landing a conviction for the prosecution. The suspect is sentenced and sent to prison.
While this makes for excellent television dramas, forensic evidence is actually much less reliable than many people in Minnesota may think. It turns out that the forensics that many of us may have thought would serve to close a case can and should be challenged. A criminal defense attorney can help to fight against a conviction that depends on potentially unreliable forensic evidence.
One of the pieces of evidence that many crime dramas focus on is hair and fiber analysis. While lab technicians may spend a considerable amount of time examining hairs or strands of fiber, it appears that these materials can’t actually be traced back to a single source. It seems like it is impossible to eliminate any other source of a fiber just by looking at physical characteristics such as length, color or shaft thickness. And the only way to tell if a hair is from a suspect is by performing a mitochondrial DNA analysis.
Even DNA analysis, one of the types of forensics that many people in the Twin Cities would think could solve a sexual assault, may not be that reliable. DNA tests will only work if the DNA samples are handled properly and protected from contamination. If either sample is damaged or contaminated a forensics expert may misinterpret or obtain faulty results. There have even been police departments that have shut down their DNA divisions because of consistently erroneous results.
Being charged with a sexual assault is definitely serious, but just because a prosecutor has forensic evidence against you doesn’t mean that he or she will be able to convict you.
Source: The Washington Post, “How accurate is forensic analysis?” April 16, 2012