How reliable is forensic science?

Forensic science is under fire for a lack of reliability.

The plotlines for popular shows like CSI or Law and Order almost always end nice and tidy. A heinous crime is committed, evidence is gathered and the bad guy is caught and prosecuted - all within an hour. Unfortunately, what is designed to provide an enjoyable form of entertainment has resulted in unrealistic expectations. It is not uncommon for jurors to place high levels of trust in forensic evidence as a result of these shows. The American Chemical Society (ACS) notes that the phenomenon is so common it even has a name: The CSI Effect.

Unfortunately, reality is not as tidy as these plotlines. Evidence is not always readily available and the evidence that is gathered may not be accurate. Many pieces of evidence, like fingerprints and blood samples gathered at a scene, are circumstantial. This basically means that they are not nearly as reliable as they are depicted on television.

In addition to unrealistic expectations of accuracy, more and more stories are coming out involving faulty forensic evidence used to support criminal allegations. This evidence has resulted in the wrongful convictions of countless individuals. Examples of the types of evidence that are not nearly as reliable as once thought include:

  • Fire analysis. A piece by Scientific American back in 2015 brought attention to the fact that fire analysis was "filled with junk science." One example used to highlight this point involves the use of burn marks on the floor. This is often used to support the contention that a liquid was poured on the floor to ignite the flames. However, experts note that any fire that is hot enough will result in similar burn marks on the floor.
  • Blood samples. One way to test for the presence of blood is to use a solution of luminal and hydrogen peroxide. If blood is present, the iron found in the blood will react with this chemical mixture and result in a blue glow. This appears to be an easy way to test for the presence of blood at a crime scene. However, other substances can also a result in the same reaction, creating a false positive result. Bleach is one example.
  • DNA. The use of DNA samples can provide a fairly reliable source of forensic evidence However; these samples are often contaminated and can degrade over time.

The validity of forensic evidence is also impacted by the technicians who are responsible for the evidence. Case after case has emerged of technicians intentionally contaminating the evidence, receiving inadequate training or otherwise mishandling the samples. This can result in faulty evidence used to support criminal charges against the innocent.

As such, those who are facing criminal charges are wise to seek legal counsel. An attorney can advocate for your interests, building a case to better ensure your legal rights are protected.